Presumably, you're employed. If so, you may want to first speak with a mortgage lender, ask for some tips on how to get started. Chances are you'll be advised to cut back on your spending and start saving.
If the problem is that you have a low score, there are tips on myfico.com that can help.
You can start building your credit by getting a gas or store card and keeping a small balance. This will report on time payments and build credit. Additionally, you can often apply for a home loan even with no credit. If can document 3 accounts that have been paid on time over the last 12 months (cell phone, utlities, cable TV, etc...), we can build a non-traditional credit report.