Please think about my point of view: I dont want to play automatch games because my rating will be ultra terrible due to me being only a beginner, so I go to custom games to learn the basics without having to start out with a 0-50 record. Plus my teamates will really hate me if i screw up their ratings. I just want to play, learn, and enjoy....
So automatch is exactly where you should be. Theoretically, the game will match you up against opponents of like skill level. This doesn't happen in practice, but you will be able to at least avoid premades.
But what do I hear? "OMFG NEWB WTF GTFO!" Every single game... People never say, "Oh, hi, welcome! here let me give you a few starting-out tips!" Nope. My own teammage trash talk and badger me until I leave and then when I leave they still blame me for ruining the game. This community is extremely hostile.
Don't join games that say "pro only"?? I say that tongue-in-cheek, but you would be surprised at the number of people that can't read. If you want a beginner game, host your own game with "beginner" in the title. Sure, you may get some games with people that just want to stomp, but on the whole, beginners should be joining your game. And if you really know nothing about the game, play single player for a bit.
Finally, if you are serious about soliciting tips, fire up the chat window outside the game and start asking. I would be more than willing to play a 1v1 game with you and give you whatever limited help I can provide. I don't do it during a game because most people take it the wrong way.