In addition to the changes than can change your credit score, it should also be noted the score before changes is also taken into consideration when an impact occurs. The higher the score is, the more the negative information impacts it. For example, a 30 day delinquency for a business with a credit score of 90 will see a much larger drop than a business with a credit score of 60.
As you can see, there are many factors that can change your score. As long as you are on time with your payments, keeping credit balances low, and not opening or closing accounts unnecessarily, you should not see excessive variance in your credit score.