I don't think anyone can give you "hard numbers" or rules of thumb for that, unless of course you find an FMC geek, or an engineer from Boeing...
Disclaimer: I was once "an engineer from Boeing..."
There are actually many rules of thumb that you can apply, but many of them apply to specific airplanes. Though they may work to some extent on your airplane, you'll have to experiment if you can't find any recommendations in your airplane's Flight handbook. Among those rules of thumb are:
Increase/decrease TAS by 40% of head/tail wind
Increase/decrease IMN by .001 for each 10 kt of head/tail wind
In any case, minimum speed will be max endurance (holding) speed. Maximum speed will vary with the airplane, but will be at a point where the drag curve starts rising more steeply with speed. In one airplane that normally cruised at .70-.72, max was .80; in another that cruised at .83-.85, max was .88 (in both cases, that "max" cruise was well below Mmo).
If you have an FMS, you don't need a rule of thumb; just fly ECON! Use CI=0 for most fuel savings, or as directed by your company to approximate lowest overall operating cost.