^ Word! (yay, keyboard).

Before I overwhelm you, I'll put you onto the number 1 guide for noobies: Welcome to Dota, You Suck | Purge Gamers

Nothing I say here will come close to what that guide will teach you.

Favorite Build Site - dota2alttab.com. It's just meant to be a quick site you... (SPOILER)alt+tab to. Their builds can be a little weird sometimes, with the reasoning not apparent at first, but for getting a quick handle on a hero you just randomed, it's pretty indispensable. They should probably change the name to dota2shifttab.com since we're all using the Steam overlay :P

Laning Phase Metagame - the metagame right now for 80% of the pub games you'll find is "2-1-2", 2 on each of the outside lanes and one in the middle. In higher skill games like Captain's Mode and sometimes Single/Random Draft, you'll see either a trilane on the safe/long/gank lane (top for Dire, bottom for Radiant) or a jungler, with 1 hero soaking up undivided XP in the hard/off/suicide lane (bottom for Dire, top for Radiant). In Dota 2, the long/safe/gank lane is where its easiest for that team to get kills, since a hero can move through their jungle unseen to gank, and get behind the enemies without them seeing. It's very unlikely that the other team will do it in that lane, which is why it's their hard/off/suicide lane.

Jungling - There are a lot of junglers, I think the most natural ones are probably Enchantress, Chen (very hard hero), Enigma, Nature's Prophet, Doom, and Lifestealer. Bloodseeker and Ursa are two AGI carries who can jungle, but you should probably look up first how to do it, I really don't know myself. I jungle with the first few, they can be pretty fun.

Starting heroes - KH Cloud named some good starting heroes, but I would avoid them because they're all AGI, agility heroes, carries. I'm sure it's the same in LoL, but a balanced team wins 95% of the time, but because Carries are the badass heroes who rack up the insane multikills and win the game, everybody wants to play them. In pubs you can get 3-4, 5 carries on a team and that can be an instant-lose.

Generally, INT heroes are typically played as supports, and are very powerful in the early game, STR heroes more or less qualify as gankers, and they excel in the mid-game, and AGI heroes can be very weak in the beginning, they're dependent on items to get strong, but they dominate the late-game. That's just a rough outline, as there are INT carries like Outworld Destroyer and some AGI heroes are best played as supports/gankers, like Vengeful Spirit. And quite a few STR heroes are the best late carries in the game.

Good starting heroes: Death Prophet, Crystal Maiden, and Ogre Magi for INT. They're very straight forward, you just gotta watch your cooldowns, and the first two are ranged, which is a big advantage during the laning phase. Buy your team's courier, pick up observer wards an ward the jungle/river every few minutes, and help your carry get last hits. Suports win games.

Earthshaker, Skeleton King, and Tidehunter are great STR gankers for newbies. Earthshaker is stuns, stuns, stuns; Skeleton King's ult is a passive that resurrects him as long as he's not on cooldown; Tidehunter is the best initiator in the game, his ult is a long stun in a huge radius. They're also very straightforward, use their abilities to gang up on weak enemy heroes, creating unfair 3v2 or 2v1 fights and your teammates will love you.

KH Cloud covered the carries. Sniper would be my favorite out of the three, as the other two are best when you animation cancel/orb-walk/whatever it is you call it when you attack more times than you're really supposed to. Sniper just needs to get a heavy damage item like Desolator and that's it.

There's a lot to go over, but I'm sure a lot will carry over from LoL... we should get some games in sometime