Pants Hemmed

Taking pants to get hemmed?

If I take in pants (dress pants and jeans) to get hemmed, do I have to measure them before I go and mark off where they need to be hemmed or will they get me to put them on and do it when I get there?

I always take along another pair of pants that hang to where I want them to, and have the seamstress use them as a guide.

How to Hem Pants