Tips for Jungling?

I may be new but please allow me to put in my two cents even though it is just theory at this point.

Jungling, to me, based on what I've seen/read ( streams, uploaded videos, guides and champion pages ) seems like it is all about planning ahead: In the next 30 seconds are you going to be ganking a lane or securing a buff for your team? Which member of your team will benefit most mid or late game from you feeding them vs. which member of your team is going to need the most help to make it out of laning phase and which course of action will give your team the best result? It is all about planning ahead based on your best estimations and instincts. You'll also have to base your plans around not just your team but the enemy team and the actions they make which are often beyond your control.

Your primary agenda in the early game will be buff control; how to keep the buffs on your side of the jungle from being used by the enemy. You want your team to benefit from them so they can preform better and give your team the edge. After learning how to manage your side of the jungle successfully you can learn about counter-jungling.

Your secondary agenda in the early game, granted still very important, is learning when to gank ( "ganking" is the art of popping into a lane to help secure a kill and/or objective for your team/deny one for theirs ( keeping your buffs safe seems like it takes priority ) and how to get the most out of it.

Just as their are different types of AD/AP carries ( burst damage carries, sustained damage carries, etc. ) it seems you can also choose from multiple types of junglers: protectors, gankers and controllers.

Protectors ( farmers ) are those junglers ( , ) that excel at farming their side of the jungle making it harder for controller-types to take their camps. When they've cleared all the camps on their side they'll often gank or base to buy items before going back to the jungle to continue farming in an attempt to become a late-game threat.

Junglers geared more towards early/mid game ganking ( ) tend to have a lot of CC and mobility to set up kills for their team mates early so they can snowball at the expense of their own development. They are a decent choice to play against protectors because protectors will often be farming and unable to respond when gankers try to gank.

Controllers ( , and ) are those junglers who excel at counter-jungling, counter-ganking and seizing neutral camps/objectives such as dragon, baron and towers.

Again, I'm new and I can only go off of what others have said/what I've seen ( Youtube, Twitch, http://leagueoflegends.wikia.com/wiki/Jungling and more ) but if I were to try jungling these are the things I'd want to consider.

first find a champ that you really like that can jungle. i, myself, like warwick, diana, and hecarim. once you find your champion make a route for yourself in the jungle. Example: start with gromp cause his buff will allow you to farm the JG faster. then if my chmp uses mana, i normally go straight to Blue. i then bounce around in a very specific order to level as fast as possible, only going back to the nexus to buy items when i can upgrade. build one thing at a time. dont start your JG item then buy boots right in the middle of it. Once you start your JG item, dont buy anyhting else till its complete. Also, you dont need to smite the 'red' and 'blue' monsters to get the buff. If you want the mana/hp boost they give you when you smite then go for it. But if you just want the buff itself yo udont have to waste smite. These are a few tips i use and i hope are helpful to you

I feel like any high CC jungler works well. I prefer high CC + mobility such as J4, Vi, and Udyr.

1. Jungling - I recommend starting bot no matter who you're jungling as you can get a double leash from bot vs only top leashing you. Don't start on the buffs, make sure it's either gromp or golems. Once they're done go to your buff. ALWAYS smite red buff for your first set or two of spawns. You may think you don't need the health but you do. After buff I'd go take the closest scuttle (as long as you have hard CC as it reduces the base speed and armor of the scuttle). If you want at this point you can either level 2 gank mid on your way to your next camp (works well with J4 E/Q combo) or atleast harass them, or you could go finish off the 3rd camp on the side you started. Don't smite wolves or wraiths this early as you need the extra jungling buffs (heavy hands, poison armor, HP from red). If you're too low to do the next buff then go and grab 2nd scuttle as your hp regen should be enough to heal you while you're grabbing it. Make sure to ward the entrance to your jungle where someone could invade and steal the buff off of you. Nothing's more frustrating than red buff having 60hp left and a Lee Sin Q'ing it and taking your buff. Also try to drag your buff creep in to the closest bush as this will significantly reduce the chance that they have vision on it while also allowing you to see an incoming invade.
2. Ganking - You don't necessarily have to gank pre level 3, however it is nice and a moral boost to your laner knowing that they have a team player. That being said, don't go in to a fight while your laner is too low especially if you don't have any secondary source of hard CC. You wouldn't want to blow your mobility/CC going in and not be able to catch an Ezreal/Corki going after your low HP ADC. Red buff is your friend while ganking as it slows the enemy. It's best to bait out their flash before you go "all in". This is why it's important to call out summoner spells being blown. Try to let the laner get the kill but don't be such a nice guy that the enemy gets away. If the laner gets the kill then tax their lane a few CS. I usually just farm the current wave (don't wait for the next wave as you're wasting time you could be jungling, backing, or setting up another gank). If your ally backs then try to reset the lane for them by pushing your wave to the turret. If your laner tells you not to gank, don't gank. They usually are not team players and will screw you over even if you are just trying to help. If a lane is feeding or their opponent is fed don't try to gank for them. Tell them to turret hug and get your other lane fed. Why feed Darius a double kill when you could get your Twisted Fate some kills and have a 3 man gank top?
3. Invading/Counter-Jungling - Very few champs should have to be counter jungled or can counter jungle themselves early on. If you want to invade early I recommend you wait til minions spawn and you solo invade at their red/blue buff. Ward the bush nearest their buff. If mid lane goes missing you leave their jungle. No sense in them getting a kill/assist just because you want to get the enemy jungler behind. This is the time you either get first blood or blow off the jungler flash as they run away from you. If at red buff just make sure you can see their buff but make sure they can't see you. Smite it to kill it, this should give you level 3, red buff (the slow it vital), and fill your hp all while they're still low hp from smiting golems. stay on them unless they flash or run in to their lane. DO NOT TURRET DIVE. It doesn't matter how low they are, just don't do it. Chances are they're running to mid tier turret which shields them, or 1st tier which is near their allies then you have a 2v1. If you're just counter-jungling prioritize your smite to their wolves -> buffs -> wraiths -> gromp -> golems. Wolves are essential in not getting counter-counter-jungled. Mobile wards OP.
4. Warding - You remember that asshat who raged at you to not gank their lane? well the least you could do is ward one of their side bushes. Yeah they may not appreciate it, but you're here to win not get someone worshiping you for saving their life or getting them kills. Try to ward on the very edges of bushes to maximize vision potential (hold down the ward button and if the indicator is green it's still in the bush, if blue not in bush). Take your camera out of fixed mode and prepare that ward ahead of time so you don't sit there for 15seconds looking for the exact edge of the bush. I like to buy an early pink ward and place it in my blue buff bush. It usually lasts til about 25-30min. Scuttle is important in vision control get them when you can. The extra gold from it is nice as well. Remind your team mates to upgrade trinkets when they can and you do the same. Also remember strategic warding can be nice for a top laner (or whoever else happens to have teleport on).
5. Objective Control - If you knock an enemy out of lane take advantage of it. Push that turret as hard as you can(don't do this until after level 3, your lanes still need to farm). Blow Q/W/E/Smite pushing that lane. If they teleport back off and let your team know. Try your hardest to get dragon scuttle. Don't die for it, but it could save you from the enemy invading your dragon kill or it will let you know the enemy is doing dragon. Just keep your eyes open. Don't lose hope just because the enemy got the first 3 dragons, that just means you should try harder to get the next 3. Baron buff can be a game changer. Your team shouldn't die trying to get it, but then you shouldn't let the enemy grab it without a fight. The least you could do while they're going for it is throw some cc their way. A J4 ult to lock them in while Baron does all the damage could win you the game. Just make sure you have an escape. If you're not tanky don't try to "1V5" their team in Baron. Most people disagree and think you should never try to 1V5 the enemy but if it means they have to run from Baron or die to it then it's really a loss for them as well. If you can't contest then just make sure you ward around and push the lanes. Just remember: Baron buff grants a possible 25600 Gold lead in the form of 1.5k G and buffs. Not to mention the enhanced recall.
6. Item Priorities - Always finish your jungle item first. It's okay to buy some pots and wards but as @NewDemons says don't buy boots before jungle item. Your chilling smite works a lot better than a few extra movespeed. I like to do full jungle item (including the cinderhulk/devourer upgrade) followed by boots, some MR/Armor depending on their team comp, and item effects. I would prioritize the Warden's Mail effect over just raw HP or Armor. Other than that, do your build.

My best tip is to buy a machete.

I think almost any champ can be played in the jg, it depends on how well you pressure the map. I've seen people take Janna to the jg and it worked.