Dear Shaz,
There's more to making costumes than taking measurements. You must take measurements for garments that are listed in many sewing books. But you also need head measurements for hats, and foot measurements for shoes or other footwear. You can make up a form with the actor's name, the actor's character in the play, including whether the part is major or minor, or chorus.
If you are making costumes for a play, you need to read that play several times to accustom yourself to the characters; a long talk with the director to get the director's concept of the play is also vital.
If the play is active, it may be necessary to make two or everything, in case of damage during a performance. And find out who will be paying for the costumes--and you!
Teri