Design of a custom application

i need some advice on how to structure my application, in particular mode about design. I explain my scenario as it happens now.

A user need to insert a request of work and the system operates several functionality. This user fill a form with some data considering that he send his request to a customer on a particular branch (i.e. Customer/Branch -> SUPERMAN/LEGOLAND, SUPERMAN/DISNEYWORLD, IRONMAN/LEGOLAND). Other data need to complete the request and also to manage other rules.

In this first target (create a generic and flexible requesting system) how could i design it? Maybe a pattern could help me, but i can't see it. For example, what worries me most is all is how to treat all data (see properties) necessary like: customer, branch, request date, task and so on... I want in the end say that different customers have different business logic inside. I hope i was clear enough. Thanks