I'm not sure how many withholdings to claim. I'm single, no dependents, make $63k a year. I pay about $350 a month towards student loan repayment. Should I claim 1 or 2?

[SeanE1]

My advice would be to claim one.  When you do your taxes next year, you will see how much you owe or get back as a refund, and will be better able to gauge whether you could increase your exemption on your W-4 to two.  If you do two now and owe a lot in taxes come next April, 2018, it will not be good, so try one for now.

Also, the IRS only allows a tax deduction for the interest paid on your student loan.  There is no deduction for the principal portion of the $350/month payment.