How do I file state income tax for two different states?
I lived in two different states during the 2009 tax year. On my federal tax, my 2 incomes are obviously combined. For the state forms, they ask you to enter information entered on the federal return. However, shouldn't I only report the income I earned in that particular state for which state withholding tax was withdrawn? If so, how to I make adjustments when it asks for my federal adjusted gross income?

You should see a tax pro or invest in pay software that can handle 2 states. It's a bit tricky.
1Google for the website for the Department of Revenue for the state. California calls itself a Franchise Tax Board. You have to determine in which is your tax home: it is supposed to be where you intent to stay for over a year. In Pennsylvania, there is also a locality tax, I had to get the website for the Philadelphia Department of Revenue to get a refund form the city's tax; this was for my new client
2your tax home is where you work
3if you work one place primarily and other jobs are more or less temporary in other states those will be non resident or part time resident returns
each had income tax withheld and hopefully you can get most of it back but you have to file first
each state is different so you are probably going to have to look at their forms to see how you can sort out the income from the other state
they each have web sites and the tax forms are available on them which you can actually input the information and down load a copy