You're only tone deaf if you can't hear the difference between "God Save the Weasel" and "Pop goes the King"! Everyone else who sings out of tune is just having intonation problems.

For the great multitude of strugglers (I'm one myself)who are not tone deaf, but still hit clinkers from time to time, there's been some helpful advice in this thread. Now here's my two penn'orth.

We often hit wrong notes because we're trying to sing in an impossible key.   Each of us has a vocal range, determined partly by our natural endowment and partly by our level of training. And within that range, there's a comfort zone, where the notes can be produced with minimal effort. Untrained singers (that's most of us, folks) usually have narrow ranges, and even slimmer comfort zones. So, if we start a song too high, or too low, sooner or later we'll need a note that's out of reach.   At this point, we may quit and apologise. Or we may grab a note at random and hope it fits, or slide into another key until we break down again. The results are usually embarrassing.

So, it's vital to discover the limits of your vocal range, and your comfort zone. If you play the guitar, or some similar instrument, it can help you do this. First, play scales or familiar tunes on it and sing along with them until you run out of voice. That should tell you where your limits are. Then, choose a key for each song that puts all its notes within your range, and as many of them as possible in your comfort zone. It's likely that some songs you love won't fit into your range, whatever key you pitch them in. (But if you really like the tunes, you can always try arranging them as instrumental solos.)

Having found your key, you need to locate the correct starting note. Some songs make this easy for you. They begin on what schooled musicians call the "tonic" of the key the song is pitched in.   For those who learned the sol-fa method in school, it's "doh". Guitarists usually think of it as the root note of the song's home chord. Whatever you call it, it's easy to find - once you know what you're looking for.

However, plenty of songs start on notes other than the tonic/doh/root. These are not so easy to grab first time. And if you start singing on the wrong note, while strumming the right chord, you may find yourself singing in one key and playing in another, with interesting results. So, use the guitar to remind yourself of the starting note. Better still, work out a simple guitar phrase which leads naturally into the first note you're going to sing.   Then develop this phrase into a break you can play between verses, to give you that cue every time you resume singing.

These two tips have helped me a lot – although, like most of us, I still have the occasional vocal disaster. I hope they are helpful to others.

Wassail!