After the planning process is complete and you know exactly what you want and what you are expecting from your florist, it is an absolute must that you get everything in writing before you pay for the flowers. Your florist should draft a contract that states the exact flowers you are going to have at your wedding, the number of bouquets you are going to have (perhaps even the style of the bouquets), the price of every arrangement (listed individually, not just a single price tag if you want to be certain that you are completely covered) and the time that you are expecting the florist to arrive on the day of the wedding.
Because this is your wedding and you want everything to be just right, in the contract you may want to include things that you absolutely do not want for your flowers and the arrangements, things that you have covered with your florist and she has agreed will not happen. This way, you will have recourse in case your florist does not come through for you as she promised she would and you are unsatisfied with her performance.