My suggestion for dealing with UL is to get well acquainted with the product standard before you even call them. Most of the time, you can walk in and tell them what you feel is needed for testing, and save a bunch of time and headaches. Also by doing this, you (should) have done your pre-testing to ensure the product will pass their test.
Your engineer will become your best friend for a while, so make sure there is a good rapport. After the project is done, the engineer will step out, and the follow-up services inspector will step in. This is also a very key relationship to maintain.
There are some different rules between UL listed and UL recognized, too, so do your homework there. In general, get to know the organization as a whole, perhaps even volunteering for the Standards Technical Panel (STP) for the standard you will be using.