I will make sure I use all of these pointers as I begin hunting for vendors. Actually I still have a good amount of time left, but by looking at the concerns of all the brides and grooms-to-be I think you can never have enough time to plan a wedding.
I agree with Rudra and would like to add my view. Ask for a package then at the end of it ask them to add one more. e.g a 1 lakh package includes candid, traditional and video. Ask them to include a teaser. Remember you are paying for his talent do not goad him into adding everything.
1. Have a standard offering in mind and ask about the price for that e.g. Photography 1 day - candid, traditional and video - 3 member crew. All photographers you speak to ask about the price of this - will quickly give you a yardstick and a rationale to negotiate. The only factor that will not work here is how good a photographer is since it's at the end an "art" so, for the top guys, this will not work
2. For most of the vendor categories I spoke to 5-7 vendors and booked one. The marginal benefit of talking to more wasn't too high!
3. Do some bit of homework before you start calling - if you use the right jargon, sound knowledgable, its less likely you'll be taken for a ride