It is always a smart thing to have a plan for how you want to tackle things in business and this also means forum marketing. It will be easy to get what you want, but you should have an idea of what that is and how to use forums to get it. Successful marketers get that way by using this train of thought. First, they learn as much as possible about different marketing strategies. Then they take this information and find the best way to use it.
Of course there are some pages that are vitally important to take note of before beginning your marketing. One of which is the TOS or 'terms of service' page. This is where you'll find all the things that can make your experience a long and profitable one. If you manage to violate the terms of service for a forum you run the risk of being banned from that site permanently. They generally aren't concerned with whether or not you actually read the TOS. Part of your responsibility is to know about them so that you do not violate them. Either way, they feel like it's your responsibility to know the TOS, and it is when you think about it. If you're planning to market on the forum then you need to know and understand the terms they've established for doing so.
Don't just comment on existing threads. Start your own threads as well. Starting your own threads may be a little difficult at first due to shyness. Consider how great it is to share helpful information. Consider the information you have that could benefit the forum. Share. It's that simple. Invite others to contribute and/or ask questions.
Make a controversial statement if you're serious about inviting comments. Just be wary of crossing lines or coming across as uninformed and/or judgmental. One thing you don't want to do is start a thread that's off-topic for the forum or something ridiculous.
It is very much worth the time it takes to sit back and figure out who's who on the forum before you start to network on a particular forum. There may be a few contenders for top spot. The number of active members in a forum will have some click now influence on this too. The longer the forums have been around and more members it has, the greater the number of people who influence the forums will be. So it just depends on the particular forum, and with some forums unfortunately it can be a moderator who has this strong influence. It's usually easy to recognize the people who are 'leaders' on the forum as they are the ones others are trying to get the attention of. Once you know who these people are, then you can work to build a rapport with them.
So think of forum marketing as another form of social marketing. And it is a given that forum marketing is like social marketing. They are both based upon relationship marketing and you should become very familiar with it.