On the click, off the click.
 

I've been practising regularly with my metronome. Someone told me quite a few years ago that it was good to practise with the metronome clicks on 2 and 4. I've practised this way ever since. It occured to me today, when I was practising, that at fast tempos, where the time frame is very small, playing on the click might lock you in better. I hope this makes sense. I'm just interested in any thoughts on playing with a metronome to the best effect. In any case, that old metronome certainly helps my time.

Use the metronome in whatever fashion helps your playing. Personally, I've never heard of anyone practicing with the click on 2 and 4, but whatever works...

The metronome on 2 and 4 is quite a common practice in my experience. It works like a back beat. Definitely harder at fast tempos to get going.

clicks
 

I think the clicks on 2 and 4 gives a swinging feel, great for practicing solo ideas, but when tempos are fast and you want a solid walking line straight 4 is better, but whatever works for you