Set yourself a reminder
If you need to remind yourself to do something with the booking (eg. Collect a deposit, collect a pre-order, chase a booking) use the "Follow Up" box
Located at the top of the booking details pop up screen, click into the box and select the date you want to follow up with
Click "save booking"
On the date you have selected, the booking will automatically appear in your High Priority, with a clock icon to show you that it was a follow up.
Don't forget: Once you have dealt with the follow up, open up the booking and delete the date so that it doesn't just sit in your high priority list