I just found the Daedric bow and I would like to enhance it with an enchantment. Any ideas?

Damage Speed of Strength would be good -> that way when they get to you they will be weak and/or slow

Unless you have a mod, you can not add a spell to the bow that will add any damage on strike, because it does not strike its target, the arrow does. I usually put Soul trap for 20 sec. on target, cast when used. I use this spell and then shoot my target until I get its soul.

A Deadric bow is better, but a Bonemold longbow holds a lot more enchantment. I can't think of anything really useful that would fit on the Daedric one. On the Bonemold bow I usually put Constant Effect Levitate.

I've enchanted a Daedric bow with a lightning spell. Cast when used on target, etc. Sort of makes it look like you have a bow that shoots lightning bolts and it's handy for those times you find yourself without arrows. :shrug:

Unless you've got a way that you can balance the enchantment the bow can hold you'd probably be better off with a bonemold bow rather than a daedric one. Although, if you're particularly fond of it, I'd go with paralyse on strike or drain health.

all mentioned sound like good ideas. and you do have to keep your style of play in mind, too, so something that fits your fighting style if you plan use the bow for fighting. so anything that aids your combat and negatively effects your opponent is a go. increase skill Marksman(if you have the spell(Tribunal and or Bloodmoon only though, i think, as increase skill is not available enchants on anything in standard not expansion-ed game)).

Best bow enchantment is none. Keep the daedric bow as a souvenir and enchant a ring or amulet with CE bound bow. You then get a bow with +10 marksman (more than you can fit on any bow) which weighs nothing and can be repaired by reequipping the ring/amulet.

Yep, and remember that the "Bound..." spells only cost 10 enchant points, so you can enchant a 40-point item (like an exquisite belt) with two of those (since the first effect doubles in cost when you add the second, for 30 points total). Adding Bound Gloves or Bound Helm (especially the latter, for +10 on all armour classes) is a very neat item indeed. My first ever self-enchanted item was a constant effect Belt of Daedric Defence doing just that. Until you end up with an ebony or Daedric helm, or want the extra enchant capabilities of a Telvanni Cephalopod helm, there's not much better.

fortify marksman constant effect

How much ench capacity does the Daedric Bow have, i think 15 or 10. Not much of enchantments will fit there probably better to just use a bound version, which has a built-in 10pt marksman constant effect already. Or use a bonemold bow, it has 40 ench, in my opinion the best bow in the game.

i wouldn't bother enchanting a bow either.
just enchant something else instead and buy yourself some area effect arrows