Many modern yoga classes are structured around downward dog and other weight-bearing positions on the hands. This requires strong and sometimes flexible wrists. To keep your wrists happy and healthy over a long-term yoga practice you must practice good alignment. I also recommend Second, stretching the wrists and forearms in the inverse placement. Because of the repetitive movements and positions in yoga, counter stretches act as a safe compliment to your yoga practice.
Whenever performing a weight-bearing position with the arms, support the wrists by taking the following steps:
When aligned as above, more weight will shift forward in your hands through your fingers. This should remain the case in all yoga poses on the hands, including as you move forward from Downward Facing Dog into Plank (I often observe the inner heels of students' hands uprooting here).
Effective counter stretches
A simple counter pose is to flip the palms up, so the wrists bend in the opposite position needed for plank pose. In a seated position on your heels, place your palms face up in front of your knees, with your fingers pointed towards your knees. To modify this exercise, let your pelvis lift. When you want more depth, hang your hips back down to your keels and straighten your elbows more and move them forward away from your body. (If you have knee problems, place a blanket between thighs and calves.)
Another great wrist and forearm stretch to implement is the southpaw, in which the hands are placed palm down and backwards. On all fours, your fingers point back towards your knees.
I hope this helps you keep your wrists happy over the long haul of your practice.