1. Mortgage interest credit is a low income program. If you didn't apply when you bought the house (and jump through a lot of bureaucratic hoops to get it), then you have nothing to claim now.
2. Mortgage interest is deductible, it has its own section on the Deductions and Credits page. Are you jumping around and not going in order? You can miss things that way.
3. If you itemize deductions, you can deduct state income tax or state and local sales tax but not both. If you live in a state with a high income tax, there is no point in even testing the sales tax deduction. If you live in a low tax or no tax state, you may want to use the sales tax deduction. When claiming a deduction for sales tax, you can either use the standard amount (a standard tax allowance calculated by the IRS based on the sales tax percentage where you live and the IRS estimate of your disposable income), or you can claim the exact amount of sales tax you paid during the year. To use the exact amount you must have all your receipts that you plan to claim, in case of audit. I don't know the breakdown on using the standard allowance method or the receipt method, but most of the times, IRS standard allowance methods are fairly generous, and unless you have oversized spending for your reported income, the standard allowance method will probably save as much as the exact method and its a lot easier to claim.
4. A new roof is never a tax deduction. Instead, it is an improvement to your property, which increases your adjusted cost basis and may reduce the amount of capital gains tax you must pay when and if you sell. Keep track of improvements with your other important house papers for as long as you own the house plus 3 years after selling.
