Pls suggest

you have to:

-play more and more chess at your club

-have a little idea about openings, the main lines are sufficiant

-try to resole puzzles they improve your imagination and your tactics

Well I haven't been over 2000 for all that long myself but I find the best way to get to about 1800 is just to play solid chess... be careful!  Don't leave pieces hanging, make sure you understand what your opponent is up to, etc.

Playing lots of chess is often enough to get around there.  After that a more systematic study is needed.  If you're above 1500 or so... I'd strongly suggest How To Reassess Your Chess by Silman. ... it helped me significantly.  Keep in mind, however (and I was just punished today for overlooking this), that strategy books provide principles... sometimes these rules need to be broken (but a lot less often than the average person thinks!)... it doesn't really matter how strong your pawn center is :P.. if you've just missed a perpetual check on the wing you won't get any better than a draw :P.

But yeah.. silman, read it :P.  Once you get a little better I'd also suggest My System by Nimzovich... not because it's a great book (it's not even that good) but because he'll get you thinking about complex systems and such on your own.