League of Legends

[Kaden]

Flat Armor aren't awful runes. Give you a nice bit of early-game survivability. There are some "standard" rune choices depending on the type of champion you go with. Melee DPS most people go with Armor Pen reds, Dodge yellows, and MR/level blues. For Casters, MR Pen reds, MP/5/level yellows, and CD redux blues. Tanks are a bit more versatile; my tank page is Armor Pen reds, Armor/level yellows, and MR/level blues. I run flat HP quints on all my pages, which isn't uncommon. Armor pen, MR Pen, CD redux, and attack speed quints are also relatively common amongst pages.

What you definitely want to do before buying runes is figure out what type of champions you like to play (caster or melee carry or tank or whatever) and focus on buying runes to fit that. Also figure out why you want a particular type of rune. Flat HP quints, for example, give a pretty significant boost early game, but end up being largely irrelevant past level 6~7. Make sure you know why you want a specific stat so you don't end up buying half a set of flat runes when you realize you really wanted scaling. That's a bitch.

EDIT: Crit can be an awesome stat early game, especially on someone like Mundo who can give himself a nice damage boost from the get-go. It's basically the only stat that's "hidden" from the other player, which can be a huge boon in those low-level fights. Getting an extra crit or two can mean the difference between first blood and a 15 second respawn waaaaay too often.