When should I file?
You should file your return as soon as possible; as soon as the IRS starts accepting and processing returns.
If you were employed, the IRS is likely holding money that is due to be refunded to you.
In any event, you should at least begin the process of gathering your receipts and getting your tax return prepared in January.
That way you will be prepared for the possibility that it takes longer than you planned to actually prepare the return.
To avoid penalties and interest charged by the IRS, you should always file your Form 1040 by April 1, or at least file an extension and pay any tax due.