Actually theres quite a bit of guessing and wrong information in the above posts :
Personal --- When you first purchase or lease a vehicle your credit reflects it and goes down slightly. Two reasons, first you have established a new debt and normally a large one. Second, you owe the entire balance so credit reports shows 25k car loan and 25k owed. The rule of thumb is to get these down below 75% per trade line (each debt) as soon as possible. Now remember the more credit you have and the longer you have had it will likely reduce the lowered amount versus someone with new credit or very little of it.
Business --- When purchasing most depreciating items in the business name a personal guarantee is required. This form basically says if business fails they can in effect come to you for repayment of debt. Problem is, almost every lender records this on credit report like a coapplicant or coowner and thus effects your credit still. It does or is like to also report on Dunns/Bradstreet and this will build a history of credit for business also. The benefit to this type of lending is you can usually write off the payments as a business expense, and later if applying for additional credit most lenders will remove debt from your DTI (debt to income) ratio to benefit you.
As for anyone wanting to check credit, use annualcreditreport.com and you can pull all bureaus once a year for free. They charge for scoring however. Do not close out the oldest and highest level credit cards, these factor heavily into scoring so keep a favorite long term friend, and a clean no balance one with the heaviest of available balances.