Even when it comes to forum marketing you should have a plan for how you want to take action. It will not be too difficult to accomplish what you want, but know what you want to do and how to leverage forums. Successful marketers get that way by using this train of thought. First, they learn a lot about the various marketing techniques. Then they take this information and find the best way to use it.
Most people, maybe everyone, behave in forums according to their general personality. Others will be more extrovert or even introvert. So, unless you are a rude person, just be yourself. If you are the shy type, you don't have to start contributing right away. This is a common activity called lurking. You might be too afraid to make a first post. Begin by talking in other threads and providing useful information.
Look at the signatures if you want to see if marketing is permitted. See if the signatures have links. This is what is done if forum marketing is okay. After you have been to a couple of forums you will be able to ascertain the forum marketing rules. Plus you can also get better ideas about what is allowed by taking note of other things in signatures. For example, they might have numerous pictures and loaded with links. This will give you an indication that it's really a marketing friendly forum and you can proceed to join.
It doesn't take long to see that some people always seem to be coming up with new ideas and beginning new threads. When people start too many; it can lead to a bad impression. But, if you have a lot of good topics for threads, then that's great but just spread them out.
Don't neglect the other threads on the board. People in Your Domain Name forums are generally pretty much the same because it all relates to human nature. Even in this type of situation, you can't always navigate to these guys follow along with others just because it's expected of you. You'll have no shortage of gray areas to contemplate as you use forum marketing more and more. The best approach is to share your knowledge in as many ways as possible. In conclusion, if you have spent time doing online marketing on forums, this is probably old news. As long as you use common sense, and stick to the rules (regardless of the forum you're on), you should do just fine. Your goal is to offer value, and to contribute to the community in any way that you can.