How do I tell if I am missing any documents to file taxes?

TurboTax provides this Tax Preparation Checklist.  You may also find this document helpful.

Tax practitioners routinely ask clients to complete a checkoff list of potential tax items that they expect to report.  I have had clients do the same thing on an informal basis.  I remember one customer who made a list of documents that she received each tax season and she pulled out the list the next year to check off documents as they arrived in the mail.

Tax software routinely 'pulls over' information from the previous tax year giving the preparer a 'heads up' that a W-2, 1099-R or 1099-DIV has not yet been received.

I have learned not to be too eager to file 1099-B brokerage statement data until I am sure that corrected copies are not going to be issued.  More than once I have seen corrected documents supercede final documents released by brokerage firms.