Coming up with a reasonable budgetbefore you even begin to seriously consider vendors and become enamored with their work is a great way to begin your research. The flowers, the food, the dress, the decor - all of these elements contribute to your wedding in their own ways, from keeping guests happy to beautifying the venue, but it's up to you to weigh their importance.
A photographer is one of the most important vendors to book early on because when the wedding is over, the images allow this once in a lifetime event to live on. The cake will be eaten, the dress will be worn, the decorations and flowers will be discarded. I try to focus as much as I can on candid, fleeting moments because these are the kind that are hardest to capture and the hardest to remember once the wedding is over.