You could try the SEARCH function and type something like 'first mountain bike' ...that will bring up lots of posts. Also maybe check out the MTB review website and see what bikes get the best ratings. For about 1000 or so alot of advice I've read here recommends a hardtail. Once you find 3 or 4 models/makes that seem to be good then it's a matter of going to the shop and riding them.
If I had 1000 to 1500 to spend I would at least consider the Specialized Stumpjumper...but of course all the other makes, Trek, Kona, Giant etc. have models in this price range as well.