Signing up for a credit card does have a small effect on your credit (FICO) score. If I were planning to seek a large loan (a mortgage, for example) soon, I would be somewhat reluctant to sign up for new cards.

One step you can take is to get an idea of your current credit score and then to track it. Banks use the FICO score, but you can't monitor that without signing up for a paid service. The large credit reporting agencies (Equifax, Experian, Transunion) offer limited term free trials. I did sign up for a free 3 month Equifax trial, but found that the number of times I could check my credit score at Equifax without fees was limited.

So I am currenly using CreditKarma (www.creditkarma.com) to monitor my credit score. CreditKarma does not give you a true FICO score. Instead, it provides a Transunion score that is related to your FICO score. In comparing my score at CreditKarma to my FICO score during the Equifax trial, I found that it was generally in the same ballpark. You can check your score at CreditKarma as often as you wish without incurring fees and I think it will be a reasonable approximation of your true FICO score.

So, what I'm suggesting you consider: if you wish to sign up for credit card offers but are concerned about what effect this may have on your creditworthiness, you can monitor the effect on your credit score by tracking what happens via CreditKarma.