If you tend to start in very inappropriate keys, get a pitchpipe.

Someone recommended a pitch pipe to me, once. I don't know if I speak for other singers here, but there's an untrustworthy note or two right at the top of my range; I usually avoid singing right up there, but if I need to I can usually manage to hit it, as long as I don't need to stay there too long. A song I learned a few years ago hit those notes briefly, but gave them rather a dangerous degree of prominence. Practising, I spotted the danger and tried pitching the whole thing a bit lower, but it didn't sound - or more importantly, feel - right. To get out of the danger zone I needed to go down a whole tone; the trouble was, most of the song was much lower down, and it ended up sounding much too big and 'chesty'. I decided to risk it.

When I first sang the song out, a fellow singer commented on the dodgy top notes and asked if I'd ever considered a pitch pipe. I said No. A fuller answer would have been "Firstly, I usually carry a whistle; secondly, I'm fairly confident I was pitching that song where I meant to pitch it, so getting a note wouldn't have made any difference; thirdly, if I had started lower I can guarantee that the bulk of the song wouldn't have sounded as good, so if those top notes really were wince-inducingly awful I'm just going to have to work on my range; and fourthly, I don't think I saw anybody wincing."

Maybe it's just as well I stuck to the short answer.