To Jutsu and others, this: https://purgegamers.true.io/g/dota-2-guide/ is the updated newb guide by Purge, a reasonable good player and caster. It explains much about the game's basics.

To Jutsu and supports: Glad you would like to babysit. Just be warned, although newer players are asked to support, supporting can become very difficult and slightly stressful to play. As a support player myself, you have to mentally be prepared to sacrifice yourself, be flamed, die, or never get your core items. That being said, playing support can actually very awarding. Nice players congratulate good supporting, not the selfish carry. The feeling you get when you know you boosted the team to victory. Commendations, cause people usually commend supports. Looking at the minimap and being able to almost see the entire arena. Looking at the minimap is crucial, by the way. As a support you have the job of pinging your teammates and telling them about certain things, e.g., if.someone is missing from your lane (although everyone should do this), telling them if a Rune is available, if there is a stacked camp they should farm, etc.

About snowballing: not taking RNG into play, Dota is a very choice-decided game. For example, one team may be ahead 10 kills, and have taken all your t1 towers. However your lineup is very late game. If the enemy team does not end the game soon enough, they will be outcarried, and lose. Mentally, being in the lead by a great margin creates a sense of security, and they tend to make mistakes. The losing team would tend to be more cautious. So, if the winning team fucks up big time and gets teamwiped, the losing team has the chance to push to victory.

I'm a pro at DoTA Frozen throne. But I'm a serious noob at DoTA 2. Any tips?

Quote from Jutsu

Now, If I know nothing about DoTA. What useful information should new players have going into it?

Play Bristleback and turn around.

Quote from Jutsu

Now, If I know nothing about DoTA. What useful information should new players have going into it?

Oh, and I forgot. If you're going mid you should buy a bottle and make sure you use it keep the runes on your team. They work a lot like the altars in Twisted Treeline and are located in the river on opposite sides of mid lanes. Some items can only be bought at the "secret jungle" in your team's jungle. I'm sure the guide takes care of that though, be sure to read that.

Quote from Veir

Play Bristleback and turn around.

And remember to discard all other keys when playing him except W
Your job as Bristleback is to literally smash W and to play like Singed

Play pudge/sniper/riki/silencer/invoker/meepo and wreck newbs.

Do not play Invoker or Meepo. Or at least not yet. Invoker is basically Kael'thas but mechanically he's much more complicated (and I mean it) and Meepo relies heavily on micromanagement á la The Lost Vikings. Riki can be good for learning DotA but newbies are usually warned not to rely on his perma-stealth and become a "Riki player". As a Zeratul main however, you might find him worthy to take for a spin.

Quote from Damian

Do not play Invoker or Meepo. Or at least not yet. Invoker is basically Kael'thas but mechanically he's much more complicated (and I mean it) and Meepo relies heavily on micromanagement á la The Lost Vikings. Riki can be good for learning DotA but newbies are usually warned not to rely on his perma-stealth and become a "Riki player". As a Zeratul main however, you might find him worthy to take for a spin.

I think the fact that he highlighted them so much was meant as a warning already

Basically, Jutsu, specifying what Damian said (you can always read it on a wiki though):
-Invoker is not basically as Kael'thas (I read his skills: where is he basically like him?): he has 3 main skills which he can combine to cast different spells based on what he combined. The reason you should not play him now is that he has a total of 14 skills (3 to combine, 1 that combines and 10 that he can actually use) and for a new player that may be too much (I mean, people fuck up with champions with only 4 already)
-Meepo is close to the Lost Vikings only that he's more unforgiving: he can have up to 4 (5 with upgrade) "selves", all of them with own mana and spell cooldowns. However, from one side the Lost Vikings can still live through by having one member alive; from the other, if even one Meepo dies, they all follow (and no, he doesn't have reduced death timers unlike the Vikings (he got nerfed lately))

A real good suggestion would be to learn the basic russian language though :P

I meant Invoker and Kael'thas were the same character in virtually all respects up until the point where they changed the hero names in DotA 2, like Windrunner becoming Windranger, Illidan becoming Terrorblade and etc. They're on opposite ends of the easy-to-play spectrum, however.

Just know Cyka and you're set.

Yeah invoker and meepo were a joke. Riki is actually a good counter to many heroes, especially legion commander, clockwork, etc .