Youre score will lower only if a lending institution pulls your credit. If youre applying for a new cell phone or switching your power on at your house for the first time, they pull your credit but it does not affect your score because they are not actually loaning you money, just determining if you are a risk. Also, checking your score does not affect it.... but it does show up as an inquiry. When you check your score at Equifax, they will have two categories.... one for lending institutions (ie. banks, car loans, credit card applications) and the other for non-lending inquiries like power companies and such.
Im not exactly sure how many points are deducted when a lender pulls your credit, but its a few points. You never want to apply for a credit card just to receive a free t shirt or tote bag.... thats an instant point deduction. You do want to have a credit card or some sort of revolving credit to show that you are capable of holding credit, but the trick is not too much credit. Having too many credit cards or loans can make you a higher risk and lower your score because you could possibly be on the edge of your credit envelope, and the banks dont like that. Its all about your debit to income ratio and paying on time.
We had a client a few years back that was pre-approved for a $250k home loan. A week later he decided it would be a neat idea to buy himself a new car to celebrate, needless to say the underwriter now saw him as a higher risk and declined his home loan. If he would have waited till after he closed on his home loan to buy the car he would have been ok.
The credit rating game is a tough nut to crack, but once you get the hang of what to do and not do it doesnt take as long as people think to raise your score. There is plenty to read up on online about how the big 3 come up with the ratios to determine your FICO score. I have been saying for years that our school systems need to have a class that teaches kids about credit and how to maintain good FICO scores. This should begin being taught at least in 11-12th grades to start. Without good credit youre dead in the water, or at least be prepared to be renting for a long time.