Search the net, I know ebay comunity where giving away $20 coupons for adwords.

Just look out for similer things like that I do, because I'm going to be paying for adwords anyway I might as well...

The best way to get people to forums is to register on other forums and post for a while as a normal user. When you have built up a rep you slowly drop in your link as if you've just found it.
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That would depend on a lot of things;

Adwords is just a auction for keywords, if you bid high you get the best position but just like any auction if no one else is buying you'll get keywords...