I'm thinking of taking on a "side hustle" to supplement my income. I'll be a 1099 contractor. How do I file my taxes?

To report your self employment income you will fill out schedule C in your personal 1040 tax return and pay SE self employment Tax. You will need to use the Online Self Employed version or any Desktop program but the Desktop Home & Business version will have the most help.

For the future, There is also QuickBooks Self Employment bundle you can check out which includes one Turbo Tax Online Self Employed return....
http://quickbooks.intuit.com/self-employed

You need to report all your income even if you don't get a 1099Misc. You use your own records. You are considered self employed and have to fill out a schedule C for business income. You use your own name, address and ssn or business name and EIN if you have one. You should say you use the Cash Accounting Method and all income is At Risk.

After it asks if you received any 1099Misc it will ask if you had any income not reported on a 1099Misc. You should be keeping your own records. Just go through the interview and answer the questions. Then you will enter your expenses.

Self Employment tax (Scheduled SE) is automatically generated if a person has $400 or more of net profit from self-employment. You pay 15.3% SE tax on 92.35% of your Net Profit greater than $400. The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare. So you get social security credit for it when you retire. You do get to take off the 50% ER portion of the SE tax as an adjustment on 1040 Schedule 1 line 27 (goes to 1040 line 7). The SE tax is already included in your tax due or reduced your refund. It is on the 1040 Schedule 4 line 57 (goes to 1040 line 14). The SE tax is in addition to your regular income tax on the net profit.

Here is some IRS reading material……

IRS information on Self Employment
http://www.irs.gov/Businesses/Small-Businesses-&-Self-Employed/Self-Employed-Individuals-Tax-Center

Pulication 334, Tax Guide for Small Business
http://www.irs.gov/pub/irs-pdf/p334.pdf

Publication 535 Business Expenses
http://www.irs.gov/pub/irs-pdf/p535.pdf

Taxwise  it is not difficult.  When you tell TurboTax that you have a 1099-misc  to report, it  will ask questions  to be able to fill out  Schedule-C --- your gross income ( amount shown on  1099 -misc  box 7  -- Non-Employee Compensation ) and then you get  a chance include all the expenses  associated with this income stream ( such  as mileage ,  etc. ).   Note that you will pay two different   types of taxes    (a)  federal & state income tax on net income ( after  expenses )  and (b) Self-Employment Taxes  (   called SECA  and equivalent to the total FICA taxes  , 15.3 %   of  approx 92% of net income). There is also an adjustment of 50% of the of the SECA to your gross income  i.e. your net  misc income is reduced by 50% of the SECA  tax,

TurboTax will do all the work for you once you enter the 1099-misc, but you should be aware of   (a)  the  SECA and the chance to deduct expenses associated  with the income   and (b)  that you will have to make  quarterly estimated payments  for federal  ( including the SECA )  and State taxes.

Hope this answers your query