YJ's suggested practice 'areas' are good choices, and it is important to note his advice to fire each iron being 'dialed in' in both directions - down the fairway, then a reverse shot going back to where you first played the club. Note distance carried (and roll) in both directions, then average the results; it's that average carry/roll number that should go in your notes.
Practically, you can't practice anywhere with zero wind and elevation changes, so trying the shot both ways should effectively cancel out wind and elevation differences. To be more thorough about gathering this kind of info, repeat the process with no spin, 1/2 back, and full back-spin.
Do not neglect the other shot types: Punch, Pitch, Flop, and Chip - the latter 3 being mostly limited to your wedges. Do the same process as above, varying spin to analyze impact on carry vs roll ratio.
Ultimately, you can add intentional off-ding data (thanks Cerino, for jogging my memory) if you intend to add draws and fades to your game arsenal. Adding these shots to your bag is a valuable tool, but going the 'shot-shaping' route will cost you distance, relative to a dinged shot. I now have an idea of what the 'distance penalty' is for the amount off-ding I hit. As a % it varies with the club choice and shot type.