I don't know if this helps, but out of college, since I used no credit cards in college, the first credit card I applied for I got rejected (no credit history) despite the fact that I had my own checking account paid bills on time, etc. So it was suggested to me to apply for a store credit card. So I used and paid off a store credit card, and after a year or so, applied and was accepted for a regular credit card.
I have a friend who did the same thing; unbelievably she was in her late 40's and never used a credit card, so had insufficient credit history, but was planning on getting a mortgage and needed a credit score. She also got a store credit card, used it regularly (charging small amounts and paying in full) and then got a regular credit card, and then the mortgage. This happened over a 3,4? year period of time.