Here's a blog you might find interesting to read:
I myself am also going into concept art, and have been working on making myself my own little 'projects'. I also read somewhere else (don't have the link :C ) that working on a portfolio for concept art it's best to make a project 'set' of illustrations - like character lay-outs, environments for those same characters, clothes for that same universe, etc.
And if your school has some kind of art club or a game design club, that would be an excellent place to have fun and maybe have some contests to participate in.
Other than that, draw every freakin' day! And play as many games as you can. :B Conceptart.org has lots of resources for artists that is worth checking out. Also, if you aren't already, find and collect concept artists that you look up to - I find some inspiration is always helpful.