Website Promotion on Forums

I want to promote my website http://fit-and-slim.com on various health forums, such as following:

http://www.jefit.com/forum
http://thegreenparent.co.uk/forums
http://www.socialslimmers.com
http://www.shapefit.com/forum
http://www.minimins.com

Needed to write valuable information on forums and leave links to my website. Only quality work, valuable posts, no spam. In general, needed to increase my website authority at eyes of forum members and gain a forum traffic.

Here is not a quick work project to write something and deliver, I need someone to work weeks or months for that. I need person which is really familiar with forum marketing approaches, familiar with health / fitness topics, and which are really know what to do to gain traffic for my site.

Here is not a task where I can exactly say "what to do", you rather decide yourself what to do the best.

With good worker I will work on regular basis