Your apology will be more meaningful if you take the time to get together with the person whose birthday you forgot, as opposed to sending a text message saying, "Oops, happy late birthday!" Offer to take him out for lunch, and once you're there, let him know you're sorry that you forgot his birthday. You could say, "I've been preoccupied lately with my new job, but that is no excuse for missing your birthday. Our relationship means a lot to me, and it's important to me that you feel valued."

An apology means the most when it's backed up by actions. When you give your friend a gift, you're letting her know that her birthday is still important to you even though you forgot. Hand her a nicely wrapped package and say, "I wish I'd had my act together enough to give this to you on the actual day of your birthday, but I hope you'll accept my apology for forgetting and enjoy your gift today instead."

In her book "The Power of Apology: Healing Steps to Transform All Your Relationships," Beverly Engel says that a critical part of apologizing is to remedy the situation so that it does not occur again. Let your friend know that you won't let him down again the next time his special day arrives. Say, "I was disorganized this year, and the result was that I let a really important day go by. It made me feel simply awful, so I made sure to put an alert on my calendar so I won't miss your birthday again next year."

If your friend lives far away, getting together might not be feasible. On her personal website, counselor Elly Prior notes that writing a letter of apology is entirely appropriate. In the case of a missed birthday, consider writing your apology on a birthday card and sending it along with a gift card to your friend's favorite coffee shop or department store. All you need to say is that you're sincerely sorry you missed her birthday and that it won't happen again. And, of course, "Happy birthday."