The backlinks I like to use is my top keyword phrase "Post Free Ads". I saw a great change in serps when I got this idea, or am i just lucky?
Oh, it definitely helps. Be careful not to "link bomb", though. If all your backlinks are "Post Free Ads" instead of "Company Advertising Classifieds" Google might penalize you if you get caught. So, go for it but don't rely wholly upon it--use your title/other keywords as well.
Using your keywords (and variations of them) within anchor text both ON and OFF your site helps immensely with ranking. Getting people to link to you using your preferred anchor text, is a whole other story though.
That question has been asked many times, but here's one example: http://forums.digitalpoint.com/showthread.php?t=612234 Do a search and you could probably find more.