Here are some things you should know:
Bases typically vary depending on the bonus or commission possible to equal the total amount of pay annually. Managers know the approximate numbers. Ask them compensation questions until they give you some real math to consider. Finding out how successful your predecessor was (if there was one) can help you to know how successful you may be in your sales area.
Do you feel confident in the product? It has to be something you would back above other products. One or two features questioned are ok. What are others saying to overcome those objections? If you are struggling trying to convince yourself it's a good product, move on out of there.
Is there a lot of opportunity for you to get the product into accounts? Where can you get fresh leads? Have they already been 'touched'? Has there been a representative in the territory? When were they last active with current accounts? All of these questions are vital in the interview process and information that you need to know to make an informed choice about your new sales job.
Do you have a question about interviewing for a sales job? Fire away!