Sprite Stitch Board!

Probably has been asked before.

Does anyone have good simple tips to prevent bunching & puckering in your cross-stitchery?
I thought I was doing well without pulling tight, but my pattern has so many single stitches spread out, my spanning threads have out-weighed my diligence.
I was thinking about placing my little finger under any spanning thread and allowing subsequent stitches to pin it down, or actually cutting groups of spanners (of course then I'd be afraid of stitches coming undone).

To a degree, you can fix Some of this in post-production, by doing things like ironing your project well. It won't fix it 100% but it will significantly reduce how obvious it is to eyes that aren't yours (I have yet to find the solution that lets me forget errors when they happen so I don't notice them).

Your instinct to hold the spanning threads down is a good one, and one I do all the time. It's difficult if you're not stretching the fabric to have this be consistent, but if you are going to be going over the spanned area, you can work on fixing things then too. I wouldn't cut spanning threads unless they are really huge- huge enough that you can easily tie off both ends. Otherwise you might find those threads working their way out of the project. It could be that you can get away with cutting once its finished, but you'll have to decide that yourself.

I agree that you shouldn't span over too large of an area. Using a hoop or scroll to keep your fabric taut will also help with your project not puckering.