First time in the Excel Section... Be gentle please!

I have a spreadsheet which lists all visits by all clients. With this
information, I wish to create a report that lists the most frequent visitors.
I think that the best way to do this is to group the client visits so I can
see how many visits each client has made and then sort the clients by this
number of visits. I really don't know where to start on this!

Any help please?