The expenses you can deduct are listed on lines 8 - 27 in Part II of Schedule C. The instructions for Schedule C explain these different expenses. Also, Publication 334 provides detailed information on the different expenses that are deductible. The links to these items are below:
Pages 31 - 39 provide guidance on expenses - http://www.irs.gov/pub/irs-pdf/p334.pdf
If you are going to deduct mileage then you need to keep a daily mileage and expense log. Publication 463 explains the details of maintaining records and has a sample log on page 35.
Are your total itemized deductions on line 29 more than your standard deduction ($10,700 if married joint return or $5,350 if single)? If you are using your home for your business then you may be able to deduct some of the interest on Schedule C. See Publication 587.
See page 8 - http://www.irs.gov/pub/irs-pdf/p587.pdf