We have recently started a Question & Answers site http://www.comptalks.com/ask/ . Our blog has got PR4, but no experience in community building. Had a forum,but it got too much spam and then removed it. Looking for some ideas to promote it.
Write on forums explaining about your Q&A and why it's better than everyone elses etc. Personally invite experts to take part in your Q&A. Share questions on your Q&A to social networking sites. Q&A sites are not really community sites like forums. You should focus more on rewarding each member with achievements, prizes and so on instead of trying to create a community. Edit: remembered that I had written an article about Q&A site if you want to check it out: http://www.xmakemoneyonline.com/make-money-online-qa-sites/
Have you tried this? I also suggest participating in forums that are related to your website's main topic (computers) and whenever possible, refer to an answer found in your website.
try yahoo answer . I have used it a little bit, but not much. This is best way to do it . put your site in the sources section and give quality answers.
Use the social networking site specially Facebook marketing.Build a page and then promote it everywhere.Your friends may ask some questions on different issues and then its best to refer them to your FB page and eventually to your site.
Promote it with SEO. A lot people search with question as the keyword, for example, "how to increase breasts size?"