I always negotiate her preference of foreplay and intercourse options before the commencement of a scheduled romantic undertaking. Verbal agreements are subject to being easily misinterpreted, however. It is therefore prudent to use a simple form, upon which the signatory can tick the corresponding boxes. In this way, each party to the arrangement is assured the pleasantness which the act itself intends.
Most men don't put any though into sex at all. If you collate your data on a spreadsheet, incorporating graphs for trending preferences, she will surely be flattered as well as impressed with your proficiency in statistical analysis.