1) Do ask questions! You can learn a lot from the pros. The coordinators at these sites have done more wedding that you and usually have great recommendations. They can help understand your vision and whether it fits best with their venue. They can help with cost saving ideas and alternatives to the traditional wedding.
2) Talk $$$! We booked our venue as a banquet and not as a wedding package and saved lots of money. Venues with a hotel attached were much more willing to lower per person cost because they would get $ from your hotel guest. Corkage fees, cake cutting fees, table cloth fees...these can be unexpected budget busters.
3) Shop around! Get as much information as possible before you visit. Websites, emails, referrals, reviews, and books can give you a lot of information.
4) Visit your top 4-6 venues to truly see if being there solidifies a big YES or NO. Being there can really help you picture your day in that space. It wasn't until I walked into my venue that i knew. I walked out, took a picture of it and sent it to my fiance with the words, "i think we found our place!"