Shield from sun damage. Either use a body sunscreen on the backs of your hands and forearms, or a hand cream formulated with built-in SPF. Remember to reapply after washing - so the tube needs to be neat enough to carry in your handbag. Basically, get the habit of putting an SPF on your hands as part of your morning beauty ritual - post-sleep cleansing, moisturising, SPF-ing, etc. (Apparently, it takes 16-21 times of performing a task to make it a habit. That's less than a month, for something which is truly going to keep the years at bay)
Scrub, every week. Just as a once-a-week exfoliation does wonders for facial dinginess, so the same is true for hands. When you are exfoliating your face (and your body), scrub the backs of your hands. It helps treatment products penetrate quicker, while also instantly brightening by buffing away the surface cells.
Slap on a mask. When you put a mask on your face, put it on the backs on your hands. Couldn't be simpler. (If you're in the bath, that means keeping them above the water-line.)
Slather on a rich hand cream overnight. Last thing at night before switching off the light, uber-moisture your hands with lashings of hand cream. Conventional beauty wisdom says that it helps to apply cotton gloves over the top. That may not be correct; the cotton 'wicks' the cream off the hands. In the same way that night creams and facial oils applied at night harness the body's skin-repairing mechanism, this is true with hand creams.
Tip: Please don't forget the obvious: wear gloves whenever you're washing up, gardening, and may be even handling paper - it makes nails as dry as Sahara. If you can't bear to wear gloves while you work with papers, make sure you slosh on really oily hand and cuticle cream before and after. And don't use your nails as staple remover, to tighten Philip screws, or dig out stones from horse's hooves.... they were not designed for those purposes.