As a direct example: the forum I go to (while I won't say its name) is tailored for people who make money through advertising. In their IRC they talk about advertising and I went in looking to just make friends with them and to let them know I'm a designer, without asking for work. Eventually, one person came to me asking for work (and by eventually, I mean within hours) and after the work I did for him, word spread VERY fast about my capabilities and I've been booked since. The ONE important thing it to make sure you always keep your word, otherwise the reputation you've built declines.