tensai,
definitely get one of the galvanised ones unless u're into the chrome but from my point of view get the galvanised ones... less rust headaches.
also, notice how much u're willing to spend for the car ... say 5k? 10k / 20k or like some hehe 40k.
have in mind whether you want to bulit the car from scratch or done up car ... For me, its better to get it from someone who has already done up the car because he/she would have taken care of the bits and pieces ... that u may not want to deal with
Then u style it the way you want it to be later.
bare in mind also the engine ... and wat u want to engine to be in the future ... for example, if you plan to go for 318is engine, its better to get a 318 first then plonk in the engine later. If you plan to go for a m20/b25 (2.5 e30) then purchase one that is already 325.
Like what Kevster said, please read up more about the car from the forum, other forums, website etc and most importantly test out all the possible options (318i, 325i, 318is, auto, manual etc) before buying the car ... take it from me, if you do not ... u may end up frus to max.