Build a database and have a flood of

cashed-up customers on-demand

Type all the details into a computer

Save all those customer details in an Excel spreadsheet file, or similar spreadsheet program.

If you don't have a spreadsheet program, create a simple text file and type their details in with Tabs between the first name, last name, phone number, email address and so on.

Here are example files you can use...

Excel spreadsheet

Text file (there are tabs between each column)

To download and save them, right-click on the link and choose "Save as".

Save the files to your computer in a place where you can easily find them later.

They are exactly the same as the ones I use, but I've taken out all my customers' names of course.