I know that you could take down an archer and take their arrows but that may not always be the best, it seems to vary.
Spell Requirements:
Command Ceature - I would suggest 25, the maximum level. - (I think that this may work on some humanoid types but am not sure).
Invisibilty - Optional, but it certainly helps.
Restore Health on target - Maybe 50 points or so, you could a have a few I guess, maybe at 50, 75 and 100 or whatever.
That's it I think for the spells and all you have to do is go into any places like forts or ruins where
there are archers about and sneak up to them while invisble and command them. If there are no other foes about
I usually lead them to an area where there are some and then after commanding them, just stand back and enjoy the show.
Then it's just a case of re-commanding them when the spell wears off, collecting arrows and going invisible again etc.
It's also quite useful when you can stand behind them, as this not only provides some cover but you also can keep their health up to a good level,
making sure that those arrows keep on coming.
I have often aquired something like 100-200 arrows using this method and it is quite amusing as well.
May your kills be quick and many.