a good start is to look at peoples 10 ten charts (current topic) - and try some samples as a starting point. Most of the stuff talked about here is split into UK&European hard techno and London Acid Techno with a bit of chicago and detroit stuff chucked in occationally.

Good sites to start with are:
nuloop
music-head.de
bangingtunes
TuneInn
Juno

You can get mixes and some currenyt/back catalogue off Kazaa.

You'll need real player installed.

Peace