A mixture of both Broad and Exact Match. Exact Match is good to use when u first start a campaign as it allows you to get a higher CTR on your ads... which in turn, leads to lower bid prices on your keywords. Exact match also (in most cases), prevents you from getting killed financially if the keyword(s) you pick are bad. I add the broad matches only after I have my successful exact match keywords running... in order to get more traffic.
if you're going to broad match, watch your campaigns closely and add lots of negative keywords to keep it under control