I used to do a lot of DIY PCB's with the photo-resist method, but lately I've been getting lazy and just ordered boards ready made. For hobby projects I've been using ITeadstudio(google it if interested), because they're cheap and do adequate job, especially for the price.. 10x of these boards cost me 25$(+shipping). Of course, if you're in a hurry it's bad since china post takes ages to deliver. These boards have the smallest traces 8 mils and smallest spacing also 8 mils.. no problems in the boards.
With the photo-etch method I initially had lots of trouble. What woofer suggested regarding doing a test PCB is a good idea to get the UV exposure right. Once you find a good setting, write the numbers up. Not much good if you've forgotten the good setting next time you do it. Also document the developing solution.. Too little or too much NaOH and it's not going to work well. Also, in time the solution will concentrate, if water is let to evaporate (been bitten by that a few times as well..) Lastly, stick to the same manufacturer of PC board, I've found that the optimum settings differ quite a lot from one PCB manufacturer to the next.
Most of the time nowdays I tend to build quick one-off projects on perf board, for the more layout critical stuff / SMD boards just order the boards professionally made.. Cost is about the same for having them made for me to buy the raw materials anyways =)
edit. I always used the pre-sensitized boards, I found the spray coating of UV sensitive layer way too error prone, at least for me. Also, I remember a good advice in mixing the developer.. Add NaOH to water until the solution feels "slippery" to the fingers