I use different colored sticker dots for the various types of cues, with the number/letter of the cue written really big on it. 1/2" circles are too big, 3/8" is about right. This is REALLY useful in tech, as it's a lot easier to just peel up a sticker (or cluster of stickers) and move it, than to erase a nice, big, clear cue and line. I've found this works GREAT in musicals where you're calling off the score, as the sticker doesn't get lost in the "chaos" of the music as much as a hand written cue does, and you can put it right over the correct beat. Also, depending on how fast and furious your cues are, you can put the sticker right in place, in the middle of the text. Sure, you lose a few words, but they're words AFTER the cue, I don't much miss them.
And, the different neon dots almost glow under blue or red running lights, making them even easier to see.
Usually I end up going back over my script and neatening things up at a point once we've opened, but the stickers save so much time in tech week.