Record what changes the next decision
Exercise, load, reps, and an effort marker such as RIR are enough for most lifters. Notes matter when setup, pain, or technique changes the meaning of the numbers.
Log during the session
Entering a set immediately is more accurate than rebuilding the workout later. A good tracker keeps the previous result visible and the next input one tap away.
Review trends, not isolated days
Look across several weeks. One weak workout can be noise; a repeated plateau or drop is a reason to inspect recovery, programming, or technique.