We sold our house last year in March and did not receive a 1098 form. Maybe because we did not pay over $600 in interest. What do I put for the amount of interest paid?

Let's assume you paid your monthly mortgage payments on 1/1, 2/1 and 3/1.  Then, your final payoff figure will have included interest from 3/1 to the closing date.  If you closed a little early, you might even have gotten a small interest refund.  (For example, if the payoff figure was calculated for 3/20 and you closed on 3/18, you should have gotten a check for 2 days of interest refund.)

The net interest you paid for the year is deductible even if you did not get a 1098.  However, you will have to determine the amount yourself, either by getting an account statement from the lender (call them or use their web site) or from your other financial records (monthly statements, closing statement). 

You can also deduct property taxes you paid, but only for the days you owned the home.  For example, suppose property taxes are due February 15, and your lender paid them on time.  Since you paid taxes for the whole year in advance, including time the buyer will own the home, the buyer gave you a credit at closing for the days they would be owning the home.  You can only deduct the portion of taxes that apply to the days you owned the home (that would normally be the full bill minus the credit.).  You can deduct the taxes even if you did not get a 1098, but if audited, you will need your own records to back it up.