There are hundreds of occasions when your best friend asks for your honest opinion. She’ll want to know whether you like her new hairstyle, or whether you think she’s put on weight. Most of the time, you can easily gauge exactly how honest she wants you to be. She probably already knows that the red highlights were a mistake, and that she’d look better if she lost a few pounds.

But what if she hasn’t asked for advice? Will she really thank you for saying that she has no dress sense just before she goes to an important interview? And what would her reaction be if you pointed out that she’s drinking too much, her partner’s been unfaithful or that you’re sick of her moaning?

Before you say what you really think, these are the questions you should ask yourself:

• Are you sure about your motives? – Maybe your friend has always been one who gives advice and you can’t resist turning the tables? Have you discovered something secret that’s made you feel wonderful?
• Is it any of your business? – Consider the kind of relationship you have. You may be good friends, but are there no-go areas? Think carefully before you break unwritten rules. For example, if you both know that the one thing you don’t do is criticize the way you run your homes, then steer clear of the subject. But just because she’s always revealed the most intimate details of her sex life, doesn’t necessarily mean she’ll take kindly to unasked-for-advice.
• Will she give you a fair hearing? – There’s no point in a heart-to-heart if she’s so upset by a situation she’ll take everything the wrong way. Maybe it would be wiser to choose a moment when you sense she’s more receptive.
• Are you sure of your facts? – Perhaps the women you saw your friend’s husband kissing on the cheek is his sister or cousin. And double-check any gossip from so-called concerned mutual friends.
• Is this just a difference of opinion? – Think about what you’ll really achieve by speaking out. Will your friend’s life improve; will she be happier? Does she really need to take your comments about, say, her drinking, on board? What you think is too much alcohol may seem very little to her.
• What’s the likely outcome? – You should have a good idea how she’ll react. If you know she’ll ignore your advice, why risk your friendship? For instance, if you know for certain she won’t end an affair; maybe it’s better to offer unconditional support.
• Are you prepared for the worst? – You may feel you couldn’t live with your conscience if you don’t speak out. But you still need to consider how you’ll both feel if your honesty ends up ruining the relationship. Ask yourself whether principles are worth more than the friendship.