Chappaqua, N.Y. ? Know your joke by heart. Don’t announce in advance that it’s going to be hilarious. And never say “But seriously …” when you’re finished.

If you can’t tell a joke — or if you don’t know any — help is coming to your nearest newsstand. Reader’s Digest, which sees 35,000 attempts at humor every month, is offering several articles in its September issue to aid the humor-challenged, including “How to Tell a Joke,” “Who’s Funny Now” and its lists of the best jokes and funniest films of all time.

The jokes include some groaners (Christopher Columbus and Leif Ericsson always lose at poker because they can’t beat the Straits of Magellan).

But there are some sharp one-liners, too.

“We just really thought that people could use a laugh,” said executive editor Marcia Rockwood. “We understand how important a laugh is to people and how they really turn to us to get that lift.”

For 60 years, Reader’s Digest has been inviting readers to send in their own jokes and anecdotes. The monthly collection called “Life in These United States” first appeared in the March 1943 issue and has been joined over the years by “Laughter, The Best Medicine,” “All in a Day’s Work” and “Humor in Uniform.”

At first, readers were offered $100 — big money in 1943 — if their funny story made “Life in These United States.” Now it’s $300.

This month, the Chappaqua-based magazine is inviting readers to call in and tell a favorite joke over the phone. It will be recorded and judged and the five best performers will get the chance to take the stage at a New York City comedy club.