If you have a roll of sticky tape that's not in a dispenser, finding the end can be a pain. How-to illustrator Yumi Sakugawa suggests that you use a toothpick to mark the end of the roll.
This way it will be easy to pull back up next time you need to use it. This is especially useful with clear packing tape and other large rolls.
If you don't have a toothpick you can always just fold the edge of the tape under itself to create a makeshift handle, but then you lose the sticky edge of the end of the tape. If you can locate a toothpick, it's a much better option.
Another useful variation is to use a paper clip. This has a similar effect, works better with smaller rolls, and is more likely to be found in the same desk as the tape.
16 Excellent Uses for Toothpicks [Secrets Tips from the Yumiverse]