This is a work in progress first of all so check back because it will be updated semi-weekly. These runes will make him able to kill early game but dominate late. This guide will show you my build that I've refined from everything I've learned.

Early Game:
In a 5 vs. 5 pvp game, never ever take middle lane. (There I said it for even the most nooby of you so you won't ever do that.) Okay, now that the warning is out of the way, I can tell you that you want to try and combo you Q and W skills before going into a fight. At level 3, you should be hard to kill when doing that if they are evenly matched. Immediately after you Q hits, begin you E skill. If they are on below 150 health, hit them with ignite to pick up the kill. Do not turret rush early game. Never get caught on their side of the turret early game. Since flash has been nerfed a ton, I can no long say that is a remotely good idea. Remember! Your passive regenerates health so turret hug as opposed to going back. This is as far as I'll get right now because it is late. Give me suggestions to what I can change. And yes, I do get this build every game and finish 80% of the time with all the items. I will teach you how when I elaborate more soon!

When playing Garen, your W (shield) is great combined with your Q. After taking down their health with your Q&W combo, quickly fire your E. If it is a squishy character, that could be enough, but if you haven't finished them yet, pop your ultimate and finish them if they are on ~35% health or less.