The most important consideration is identifying the the data elements needed, and the relationships needed for those elements to present an accurate and coherent representation of the processes and facts about your business. This means you have to understand how model data.
I suggest the Filemaker Training Series (FTS), all of which is a good starting point, but in particular module 3 'Data Modelling'. Since you are a member of this Tech Network you can get an electronic download for a greatly reduced price. Also, periodically, the Tech Network publishes some of those modules for free.