How do i raise my credit rating score, if i cant get a credit card?

Im looking to buy a house in 12mths or so, but need to raise my credit rating to obtain a mortgage. i tried to get a credit card to help me do this, but was refused. what can i do?
Answer
Do you have negatives on your sheet? try fixing them first then get a card. orchard bank and household bank walmart are nice place to get cards with bad or no history