How do I figure out if I will owe taxes

Do I get a write off for paying student loans?

Maybe. See

Generally, personal interest you pay, other than certain mortgage interest, isn't deductible on your tax return. However, if your modified adjusted gross income (MAGI) is less than $80,000 ($160,000 if filing a joint return) there is a special deduction allowed for paying interest on a student loan (also known as an education loan) used for higher education. For most taxpayers, MAGI is the adjusted gross income as figured on their federal income tax return before subtracting any deduction for student loan interest. This deduction can reduce the amount of your income subject to tax by up to $2,500.

Read the whole document to be sure, but that's the basics.

You'll have to fill out a 1040 or 1040A to claim a student loan deduction. It won't be on the 1040EZ. You do not have to itemize though.

What kinds of write-offs and credits are available for someone who is single and lives in an apartment with two roommates?

As a practical matter, in 2016 you'll get the standard deduction for someone who is single ($6300) and the personal exemption ($4050). It's extremely unlikely that you'll be able to deduct more by itemizing. Most people who itemize are taking a mortgage interest deduction. Major medical bills are another possibility, but they have to be more than 10% of your adjusted gross income (it's one of the lines on your tax return). Assuming you rent and are reasonably healthy, you are unlikely to have enough to itemize.

The most likely additional deduction would be the one for an IRA (Individual Retirement Account). Although you might be better off doing a Roth anyway (no tax deduction).

If you are self-employed or making more than $100,000 a year, there are additional issues. But most people aren't. If you filled out a W-4 and will get a W-2 back, you aren't self-employed. Hopefully you have a rough idea of your annual income.

The first $9275 over your deductions will pay 10%. After that, up to $37,650 you pay 15%. The 2016 link above has a link (PDF) to the full table if you need more than that. Note that that is the first $48,000 in income with your $10,350 in deductions.

If you want to predict the, the easiest solution is to get hold of a copy of last year's tax forms and fill them in with estimated numbers.

Odds are that none of the more complicated deductions will apply to you this first time around, so I'd suggest just using the federal 1040EZ, and your state's equivalent, for this purpose. If it turns out that you can claim anything more than the standard deduction, that would reduce your taxes, so this is leaning toward the safe side.

Your employer pays the expected (but estimated) taxes for you.

So the chances are you don't own more; but that might be different if you have other sources of income that he doesn't know about (interest on savings or a side-job or whatever). Also, you could have deductions that reduce the taxes you owe, which he again doesn't know, so you overpay. If you don't file, you don't get them back.

Most tax software companies offer free usage of their tool for standard filings, and you can use it to find out your tax situation, and then buy the tool only when you want to file. If you use one of those, you can type in all your data, and depending on the result, decide to buy it and file right away.

Note that if it turns out you owe taxes, you must file (and pay), but of course you can do it manually instead of buying the tool.If it turns out you get money back, it is your decision to file - you probably don't care for a small amount, but if you get 1000 $ back, you might want to file - again, buying the software of doing it manually.