It depends on a few factors; the cause, the extent, the options you prefer to take, etc. If neck dive is bothering you, I'd suggest looking at the following options:but how are you guys solving neck dive? the ones who experience it? (I do, slightly but I do. I wish my SG balanced as well as my PRS...)
1) Reduce the weight at the headstock (lighter machine heads, light weight buttons).
2) A thick strap with plenty of grip (like suede) - though if the neck dive is strong it might just drag too much on your clothes.
3) Use your body to prevent it: Hold the neck up wth your left hand - though some find it interferes with their playing if they've got to support the weight of the guitar too much. (This is pretty much the defining issue of neck dive - you're going to have to hold up the neck to play! So if you've got a problem with neck dive, this isn't likely to be much help). Some also use the right arm to 'clamp' the guitar to their body & prevent it moving.
4) Add weight to the body.
5) Move the rear strap button, like this. (But only if your SG is a real keeper - it wont help the value).
6) Moving the front strap button the the horn tip - Iommi style. (Not sure how much this helps) (as above re-value)
7) Construct an extended front strap button (like the OP of this thread) (as above re-value)
Hope that's helpful, and no offence intended to anyone who doesn't believe in neck dive. :)