It is a common technique for a loan officer to tell his/her customer not to have other inquiries on their credit because it may cost them their loan. Although, this in rare circumstances may be true, it is usually an exaggeration by the loan officer to keep the loan prospect from shopping around. The technique used to combat this scare tactic is to get your own copy of your credit report, and shop multiple lender's with your single inquiry. You can sometimes get a copy of your credit report for free, and this is the perfect way to find out what other lender's are offering without worrying about your credit score.
The most important thing to remember at this stage of the loan process is that you are interviewing potential lenders. Loan officer's can be very skilled at making applicants fill they need the lender more than the lender needs them. At the end of every conversation, you should remind yourself that it is them that is trying to earn your business.
After you have selected some lenders from these "preliminary" proposals, this is when you will start letting a few lenders pull their own credit reports to verify the accuracy of yours. At this point you are letting the lenders know you are interested in their proposals. Make sure they understand their are other lenders still in the picture.
Lin Sasser
The Online Mortgage Shopper
A Consumer guide to negotiating mortgage loans
http://www.home-mortgage-loan-companies.info