I see this is your first post. Welcome to FlyerTalk!

I've found articles such as "What's in my FICO scores" at (http://www.myfico.com/CreditEducatio...YourScore.aspx) to be interesting reading about the factors in general that affect your FICO score. The exact formulation of the number is a trade secret, of course.

When you apply for a credit card, banks consider both your FICO score as well as other aspects of your credit history. How permissive or tight they are varies considerably. For example, Citi seems fairly generous with allowing people to open new accounts. I've opened 5 in the past year across various cards. Chase seems to have tightened up recently, rejecting applications from people who've opened more than, say, 3 accounts across all Chase cards within the past 12 months.