I'm low tech and prefer to use a notecard with a grid on it, the squares of which bear enough space for only a word or two maximum, but you can just as easily use a spreadsheet or something fancier.
It makes putting together a better summary at the end of your day a lot easier, and it also helps with future forays into time estimation since you have a clearer picture of how long things take.
It also helps show when it's time to go take a walk.