This is a very individual thing. Leaving aside time trouble which is a different issue, some even quite strong players can have total lapses. Either they trust their "blundercheck" to work intuitively and suddenly it doesn't, or their hand simply makes the wrong move (typically one they intend to play a move or two later down the line they've calculated).
I myself "suffer" from a harmless version of the latter: I sometimes
write down the move I expect to be played next instead of the one that was just played (by me or my opponent)! This quirk doesn't cost me any points, just the occasional messed-up scoresheet
Anyway, I think the minority who has a serious problem with this should adopt and train a version of Kotov's famous "Blumenfeld rule": Before making your move, look at the board "through the eyes of a patzer" and ask some simple questions. My favorite one is "How could this move possibly be a blunder"?, but you can also be more specific and ask "does my oppnent have any threats I haven't considered?", "will the piece really be safe there?", "did it do anything important where it stands?", etc.
The thing is to train a simple and very concrete routine, with some sort of "trigger" that should automatically evoke these thoughts. One logical trigger that is part of the process of moving: Train
your hand reaching out towards a piece as a trigger for Blumenfeld's rule. It may annoy some opponents if you retract your hand often, but it's worth it to avoid blunders.
The standard way to train something like this is to just practice doing it consciously (in training games, perhaps) for as long as it takes until you eventually do it automatically (i.e the Blumenfeld question(s) pop into your mind whenever you reach for a piece).
There is also a somewhat effective "quick-fix" approach to making situations trigger responses semi-automatically without prolonged training, called Implementation Intentions (
http://en.wikipedia.org/wiki/Implementation_intention). See the many papers by Peter Gollwitzer and colleagues, like:
http://kops.ub.uni-konstanz.de/bitstream/handle/urn:nbn:de:bsz:352-opus-55590/99... http://kops.ub.uni-konstanz.de/bitstream/handle/urn:nbn:de:bsz:352-opus-57036/07... I have used this method of "if-then-planning" a bit away from the chess board. It works some of the time - at least worth trying for someone trying to establish a good habit or get rid of a bad one.
Of course, those who virtually never blunder like this shouldn't bother with Blumenfeld's rule at all, since it's meant to solve a problem they don't have!