This depends upon what kind of income you have. Are you salaried, self employed, have schedule B, C, E income? It would hard to just answer this question without knowing what you employment status is. It could be rather lengthy also.
If you are salaried, pages 1 and 2 of the 1040 personal tax returns must be completed with schedule A Itemized deductions included, if you have mortgage interest, medical and dental expenses, state and local tax paid, real estate taxes, gift etc. If your schedule A is not more than the standard deduction; it is usually wise to use the standard deduction. If there are children you may have child credits etc...you do your calculations and page two gives you the amount you owe after all deductions.
You can also file short form if you have no deductions... I noticed this was 6 months ago but it was still open. I hope this helps.