I use many of my gramma's old recipes, and have often had to ask my mom to convert some of the info for me (Gramma was born in 1915).
A few questions I've had to ask my mom...
What is Oleo? (margarine)
How hot is a "medium oven" (when my mom got married, she had only ever cooked with a wood stove, my dad had to teach her how to use a gas/electric oven)
Do you think it's time to "take it off the fire" now? (my favorite peanut butter fudge recipe has that instruction, and I make sure to copy it that way every time)
My son is 19. I've been teaching him to cook since he was little, both following a recipe, following a "recipe", and by what just sounds good. He's now pretty adventurous in the kitchen, but I know he also sometimes gets frustrated with the vague ingredients/directions.