They will dress the tables as you see fit. It is a good idea to look through the caterer s portfolio for ideas and assurance that you will be pleased with the work. If you want to have special floral arrangements, you will need to work out such details with a florist and let your caterer know what you plan to do. The same goes for the cake. However, it is important to coordinate the arrival of the cake at the reception with the catering staff so that the appropriate table will be dressed and ready for the presentation.
Many caterers have their own requirements regarding payment and deadlines.
Find out what is expected of you. Of course, the more details you can work out ahead of time, the better for all involved.