Most of my clients need a week or two to get sign-off. A hold keeps their dates while they do (sample note).
The first client to ask gets the first hold. If someone else wants the same days, they can take a second hold and wait. When the second client is ready to book, the first gets 24 hours to confirm or let the days go.
Holds cost nothing. A booking starts with the deposit, and only then do the days go into the diary in ink.