It's said that it takes five times the expense and time to get a new customer than it does to keep a current customer. There's one major element when it comes to keeping customers: Follow up. After you've made a sale to a stock client, follow up with one of your promotions: a sell sheet, calendar, postcard or poster featuring your latest and most popular images. If you are traveling abroad, it's a bona fide reason to phone your buyers. They just might want to piggyback an assignment. Or if you've just returned from a trip, follow up with an offer to send them a selection of the results for their consideration. It's a truism: To keep customers, you need only do three things- follow up, follow up, follow up.