Hello there, I'm DriveThruGanks, and this is my very first guide on MobaFire. I've been playing League of Legends for about a year now, and while I'm certainly no MLG pro, I wanted to put a few things out there for anyone thinking of jungling in game. Don't hesitate to tell me where I'm wrong, give suggestions, or offer information - I'm always willing to learn and I hope you are too!
Let's get to it.

Ganking is the make-or-break part of being a jungler, and ganking well is the difference between staying viable all game and falling behind your team and hearing the dreaded 'This [enter champ name here]' for the rest of the match.

By now you must be saying, "DriveThru, get to the point already! How do I gank well?" The elements of a good gank are thus;

Is a teammate nearby to help secure the gank?
Are they close to a friendly turret?
Are they warded/are you ganking from an unwarded position?
Do you have enough health (and possibly the right buffs) to make the gank work?

There are a few other important things - positioning, like if you're ganking a [Vayne] and you put yourself between her and a wall, setting yourself up to be stunned so she can get away - but the most important thing, that many people don't realize, is this:

You or a teammate don't need to get a kill for the gank to be successful.
Did they pop both summoner spells in a panick? Better yet, did their lane partner do so as well? Did you force them to go back and give the laner you were assisting time to free farm? Did neither you or a teammate die?

If the answer to any of these is 'Yes', then your gank was successful. Remember that.