How do you track your miles on their spending per transaction?

The Milelion (a great blog btw) has collated a list of excel formulas that you can use to tabulate and track your miles here and here. I believe there's a spreadsheet available too!

On the flip side, I don't really track individual transactions - it's too much effort! Instead, I separate my spending amongst different cards, making sure that it is the best card for the spend category, and then just have a quick glance at my monthly statement. Unless it's a big purchase, it really isn't worth the effort to call, hold on the line and dispute with the CSO for half an hour.