This is a very good question, but one that requires a definite answer. While many people do believe that credit checks actually lower your credit score, this is not necessarily true. What is true, though, is that a high number of credit checks over a certain, prolonged period of time are often taken as the sign of a distressed buyer, and these will be taken into account.
When your credit is checked, it could very well mean that you are shopping around for the best deal, and there is no way around this. For this reason, many lenders count inquiries within a 14 day span as a single inquiry. So, even if you had your credit checked 30 times or more within that period, you would still only be counted for one credit check, and this will not hurt your credit.
Now, on the other hand, if you were getting 30 credit checks every two weeks for the past 11 months, then it would count against your credit, and would flag you to most lenders as a distressed buyer, and that would heighten the risk associated with you as a borrower. Checks spread over many months like this are bad for your credit in this respect.
Actually, a lot of banks go by the new 45 day FICO scoring system, meaning that checks made within 45 days are only counted as one check instead of those made within 14 days. This really helps you, as a borrower, check for the best rates without lowering your credit score at all.