Change in Income and Daughter in College

I have 1 salaried job and my daughter was a freshman in college starting in August last year.  I came to the new job in October of last year.  Prior to that I was a contractor.  I owed money on last year's taxes and this year's taxes.  I don't want to owe next year.  I'm not sure how to set up my W4 to make this happen.