I used to dump out my little baggies of letters and sort through them to see if I had the necessary letters for the project I was working on. Not anymore. Now I tear off and save the packaging and X out the letters as they are used. For packages with multiples of some letters I use a pencil and write the number beside the letter to indicate the current quantity. Now I can see at a glance how many letters are in my package without having to empty them.
If your packaging doesn’t come with a display of letters, it’s easy to print out your own.