- Let's kick-off the school year in style.
- Please drop-in to see our new offices.
- Sign-up today for the parents' group.
The problem with these sentences is that they misuse hyphens. You can hyphenate the two words if you're using them as an adjective modifying a noun or pronoun, but you shouldn't when they're being used as a verb.
- We're having a drop-in event so everyone can see the new offices. (drop-in modifies event)
- Here's the sign-up sheet for the parents' group. (sign-up modifies sheet)
- The kick-off (or kickoff) time is 2:00 (kick-off modifies time)
The world will not spin out of its orbit if you use hyphens improperly, but doing it right is the sign of a careful writer.