I deal with this a lot in my line of work. People think that because they have no debt, that getting credit will be easy, but in reality it makes things harder. If there is no history of credit usage, then what do we have to go off of to know how responsible you are with payments? If you want to build your credit quick, get at least 1 credit card and use it at least once a month for something small (ie; buy yourself lunch once a month, or fill your tank once a month) then pay the card in full when the bill comes in. Keep the balances low and easy to pay off so there isn't ever any interest to pay. I've had multiple folks do this for 6 months and increase their scores well over 50 points. Shit, even just having a credit card for a month can improve your scores by 20+ points in the right circumstance.
If credit age is the issue, then open a credit account ASAP to start building your credit age. Typically lenders want to see at least 3 open accounts and at least 1 year of credit history on at least 1 of those accounts.