Check with your family members first to see if anyone has a credit card that they are willing to add you on as an authorized user. This gives you the benefit of all their payment and credit history on the particular card. Consequently this means that they should not have ANY late payments, if they do then you are just working against yourself. The higher their limit and the lower the balance the better it is for you. Next check with your bank to see if they offer secured credit cards. If they do then this is a great tool to help your overall credit profile.
Also you can document your history of paying your rent, health insurance, or even child care bills on time, every time, for at least 12 months, talk to your mortgage professional about whether you can use any of these accounts to prove yourself creditworthy to mortgage lenders.
Remember start early, stay patient and you'll be able to see great results.