My description guesses go like this:
1. hair description - straight/curly/wavy, color,
2. age: if they look like they're in high school I pick 18 - 24. if they look like rotten little kids, but I can't put an age on them, I assume gen x and do the range up to age 29. If I think they are about my son's age I use the range up to 39. Anyone that looks older than my son is automatically 50, and everyone else is my age or older and end up in 60+.
3. height: SHORT (under 5 ft.), short like me (5'3"

taller than me (5'5" - 5'9"

, tall (5'10" - 6'), and very tall (over 6').
does that help?