Well I'm no Jungle Master but noone else has replied so I'll make a post.
One of the main things to note as Jungle is that you're essentially in charge of objective control. Jungling is fun, to me, because it is the most "free" of roles. Not being tied to a single lane and being at liberty to make strategic calls on the fly can make or break a team's success.
Some general tips:
-Superb Map Awareness. Always be thinking, "Where is the enemy jungler" you need to be thinking things like, "Okay I just finished my blue buff and Lee Sin is at top and doesn't have his blue, It's ~8 mins in his is probably up right now." So you seeing him top you se an oppurtunity to go for an easy free blue buff. Steal the enemy's blue, then give your blue to your mid laner. Bam, Big advantage for both you and mid. - AND the enemy mid laner can't even get their own blue to even the odds.
-Ganking is important but it's not everything. A good example would be Trick2G's Godyr. He's not really all that focused on ganking, he does when he can, but mainly especially early he is farming and getting as OP as he can as fast as he can (being sure that he told his team that they shouldn't expect ganks early) and then getting early solo dragons and even early 20 minute barons and such.
-Try to be aware of the enemy team's Team Comp (If they're mainly doing AP or AD dmg, if they have Lots of CC or Burst etc) and build accordingly.
-Try to maintain vision control. Even if you're not going out and carrying your team if you pick up a sightstone and a sweeper lens early on you will be an INVALUABLE asset to your team. You can save lives indirectly by just placing wards all around the map. Get into the practice of always having 3 stealth wards + 1 pink ward out on the map at all times and relocating them as strategically needed.
-Snowballing lanes can help a lot
-Watching Pro Video's of how they jungle, Their jungle paths, how they gank, how they make the decisions from moment to moment, Watching a few live jungle streams could really help. It certainly did for me.
-Research: Much like you're doing now with this post, The more knowledge you have the more power you have.... for example, if you smite the Wraiths now you get a temporary buff that lets you see enemy wards and stomp them. That's pretty strong for just smiting a jungle camp.
-Pressure lanes effectively
-Play your specific champion to their strengths, If you're a Shaco or Tryndamere you'll want to try and split push late game and force the enemy to deal with you which puts your team into a 4v4 or 4v3 if you make them send 2 people to handle you. On the other hand if you're someone like Rammus then try to fight -with- your team. Your Taunt and Tankiness can help win fights.
-Communicate effectively with pings and make sure that your lanes know when you're on your way, or when the enemy jungle might be coming. You have more free time on your hands since at a certain point it's possible to just auto attack the jungle camps and you can focus on map awareness and strategizing. Last hitting isn't something a jungler really has to worry about.
-Gank who needs it when they're being pushed against their tower. Even if you don't have a good path it's better to just SHOW UP and put pressure on the enemy and let them know that YES WE HAVE A JUNGLER AND I WILL EAT YOU IF YOU TOUCH MY 
. I've seen too many jungler just completely ignore a lane because they couldn't figure out a good way to get a gank off.
- Map Shortcuts help too, Like learning to hop through walls with champs that can pull it off.
That should do it for now. That was all pretty much off the top of my head. I hope it helps ^^
