Forum marketing is a way of directing targeted traffic to your sales pages. This is done via your signature box at the end of your post which can contain a link to you sales pages. Links are not allowed in you post just good content.
In order to get a post read and responded to you must make them interesting and helpful, definitely not just comments like I agree, in answer to other peoples posts. You need to be seen as an expert in your particular field. If you answer questions asked by others with useful answers you will gain a following.
If you do not know the answers you can always Google the question; you will gain knowledge and improve your perceived status, meanwhile gaining followers. If other members like what you say and you sound knowledgeable they will want to see what your offers are all about and will open your signature at the end of your posts; if your offer is good they will click through to your sales pages and now you have free traffic.
One advantage to bear in mind, once your posts are on forums they will continue to be read for months, so forum marketing is a long-term strategy for targeted traffic.
It is not good only posting on one forum or only only posting occasionally. To be successful you need to find several forums in your niche and ideally post daily; your avatar will then be prominent and people will be familiar with your posts.
Forums are online communities where you can chat and ask questions in your niche and answer other people's questions. Many forums are free to join and are used by people with online businesses and people working at home, maybe doing surveys or other online activities. Or in the hobby market, there will be people who follow a particular hobby, Golf fishing etc. To find forums that interest you make a Google search with your keywords and the word forum, and you should find a selection or forums to suit you.,
If you are looking to set up an online business take a look at affiliate marketing. If you find a good mentor, much of the work is done for you, you have products provided probably training, sales pages, banners etc. Check Google to find a choice of affiliate programs.
Some books you may like to read:
"Ask for the Moon and Get It!" by Percy Ross
"Awaken the Giant Within" by Anthony Robbins.
"I Can Make You Smarter" by Paul McKenna.
"Feel the Fear and Do It Anyway" by Susan Jeffers .
"Laptop Millionaire" by Mark Anastasi.
"Building an Online Cash Cow" by Anthony Barlow.
"SEO step by step" by Caimin Jones.
"500 Social Media Marketing Tips" By Andrew Macarthy