How to Find Forums

To find appropriate forums in which to participate, go to Google and type in your main keyword phrase (the high traffic/competition one), then add the plus sign and type in forum/s. It would look like this without the quotes (say we are using identity theft as the keywords)...identity theft + forums and identity theft + forum. This should give you a good list with which to start. Make sure that the forums to which you post will allow you to create a live link to your site -- either with your name or in your signature file.
When you are done researching forums, do the same thing with blogs; and again, look for sites that allow you to leave a live link. Put the good forums and blogs in separate browser bookmarks folders so that you will be able to access them easily.
Make a decision to start with one topic; learn as much as you can about that topic, then go out and post on related blogs and forums to create traffic to your pages.
SEO Tips for Forum/Blog Posting
If you are posting on blogs and forums only for SEO purposes, the strategy is somewhat different. Your posts do not have to be quite as good, because you are not trying to get traffic directly. However, as you can imagine, it makes the most sense to do both SEO and traffic generation at the same time.
It is very important when looking for good blogs and forums on which to post that you are allowed to receive page rank from your posts.
For SEO, you need to find out if the blog or forum has page rank, if older posts gain page rank, and whether or not the links from the blog or forum to your site have a "nofollow" tag. You also want to find the best pages on the site on which to post.
To identify good blogs on which to post, use this approach to your Google search: type in your keywords in quotes then "leave a comment" - "no comments." Therefore, your search would look like this: "identity theft" "leave a comment" - "no comments". You also may want to look for Wordpress blogs, many of which are SEO-optimized, by typing in "powered by wordpress."
Nofollow Tags
It is very important when looking for good blogs and forums on which to post that you are allowed to receive page rank from your posts. If a site is using a "nofollow" tag, it means that Google will not travel from your link to your site. The owners of many sites want to keep the page rank for themselves, so they automatically put those "nofollow" tags on contributors' links in their HTML -- so you get no PR value.
To find these tags, look at the source of the forum or blog by right-clicking your mouse and choosing "view source." Then do a search for "nofollow" (not in quotes). You can also use Firefox with the SEO tools installed. If you use Firefox, any links with nofollow tags will show up highlighted in red. This makes it very easy to find blogs and forums that will be good places on which to post.
After you have identified some good blogs on which to post, you will want to discover which pages will give you the best results for SEO. To find these pages, type the following into the Yahoo search bar - "site:http://www.nameofblog.com" (without quotes); the results you get will give you the highest ranked pages toward the top of the search. Go ahead and post on these pages using your username that offers a free report or your sig file, if allowed.