Use a flexible measuring tape. If you don't have one, print one off.
Bust: Go around your fullest bust, over your nipples. Keep the tape straight and parallel to the floor as possible. Be wearing a normal bra.
Waist: This is likely not where you would wear your pants. Measure your natural waist, where you would bend side to side. Again, try to make sure that the tape is parallel to the floor and straight.