Warding. An introduction.
"What is a Ward", you might say. Well, if you are asking this, you may often have games where the minimap looks grey all the time.
A ward is an item that you can use on the map. When placed, it will watch the map for you and see any enemy champions that passes by your ward!
"Gasp! It sounds overpowered! It must be expensive!!"
Not really. A single Stealth Ward costs 75 Gold, which is only 3-4 Minions worth of gold, and a Pink Ward costs 100 Gold, which is just 1 or 2 more Minions!
OR you could buy a Sightstone, which gives you all the wards you need for only 800 Total Gold! Can't afford to spend 800 Gold on that? Well, you have a FREE WARD every 120 or 90 seconds with your Warding Totem, and if you want, for 250 Gold, you can upgrade it to allow you a free Stealth Ward every 60 seconds!! Wow, that is so neat, right?
"But I need this extra gold for my Sixth Zeal!"
Whoa, there. You're playing Lux! What the h-[CUT]
Well, sure a ward costs you Gold, but there are so many neat things that they do for you! Once you place it on a map, it will provide you with so much information to: -Find enemies that will feed you (Giving you 300 Gold) -Let you know where the enemy is not (Underrated info) -Let you know where you can safely go (Preventing you from giving the enemy 300 Gold) -See where Teemo is hiding so you can kill him (300 more gold plus dead Teemo)
"But what do I do with this ward? I just wasted some of my Gold!"
Place it! There are a lot of grey areas on Summoner's Rift, especially in the Jungle areas! Place a ward in the Jungle, in the River, or in a lane where you usually have no vision! And use common sense on where to place it, you silly player! Having a ward in the Jungle is strictly better than ward-bombing your Nexus.
"I'm an ADC/Mid Laner!"
You have a FREE way of Warding or a cheap way of pumping out wards every minute! Your team needs you to ward! Besides, your team wants to win, and your team includes you! So if your team wins, you win! By that logic, wouldn't warding seem to be a great thing to do for yourself?
"Okay, I have vision, but I don't have a Zeal."
Now is the harder part of warding. You need to use the information that the ward has given you. Did you see Teemo wander into your Jungle all alone? Tell your team to go kill him! Do you see Pantheon trying to cheese a solo Dragon? Go punish him for not staying up-to-date with the Patch Notes. Is everyone moving towards Bot Lane to catch that Kassadin from your team? That means they won't go Top!
What if you DON'T see anyone? Well, that's just as good as seeing them! If it's still laning phase, and you have warded the enemy Red-side Jungle, and Jungle Warwick isn't there, that must mean he is probably near his Blue side! If you are split-pushing Top Lane against Red Team, and no one is near the Red Team Blue-side Jungle, that means you should probably get out before the enemy team Wombo-Combos you. Don't see the enemy team anywhere? They might be doing Baron, so get your whole team there and kill them at Baron.
"What about my Zeal?"
Well, if you buy a Ward, and you make use of it, you are buying free money!
If you see the enemy team at all times and/or make full use of the information wards give you, you will find the best ways to earn gold for yourself and for your team! You will know where to fight safely, where to farm safely, and where to take objectives safely! Your income will stay high, and your ward will help you get that beloved B.F. Sword, Needlessly Large Rod, Giant's Belt, or that Zeal you have been waiting all game for.
So basically, ward for your Team, use the information effectively, and you will win more and more of your games! While the saying "Don't just copy what the pros do" is very common and holds a lot of truth, this is the one exception. Ward like you are paid to do so, and keep the map lit up!
AS A DISCLAIMER: This will not always work against the following Champions:

WARD MTHERFKER WAAARD
"do I look like the support or jungler to you?"