A rooting hormone not fertilizer is applied to the bottom of a cutting then the cutting is stuck in well drained soil. misting is an attempt to increase humidity around the plant & there are MANY sustems to do that.... I often use a old windex bottle & just spray the plants several times a day the water is then at room temperature.
In addition I maintain good air citculation around the plant but NOT a strong draft.

Answers below...
Does it need a clear top ? yes, light is required for the cutting to make food for the new roots, however I don't use a top on my "cloner" as there is enough ambient moisture from small leaks etc.
 Does the water need some type of nutrient ? not really
 Does the water need to be kept warm ? it can help, depends on the type of cutting - if the plant likes warm temps, then it will like warm water...An aquarium heater can be useful in a cloner - I use one to keep the water above 60 degrees in the winter.
 Do the misting nozzles stop up easy ? Yes, even mini sprayers can clog as algae etc. build up, The finer the mist, the more likely the clogging. I have added an aquarium filter on the pump which drives my spray heads in my cloner. There are also misters for keeping the leaves from drying out (used when rooting in soil mix with cuttings which are hard to root), those systems usually use high (water line) pressure with a good filter and a timer.
 Will a fish pond pump create enough pressure for the nozzles to produce spray ? Probably too much, the cloner I have uses a pump similar to wall fountain. The spray should not be blasting the cuttings - just enough to dampen them.
 If I get some roots on the plants, do I plant them in dirt ? The new roots are susceptible to rot so you will have better luck with sterile potting type soil with extra perlite added.

Chad

Thanks, I am slowly learning

Is it best to cut off all the leaves and branches or leave a few on - I'm trying to propogate Ylang Ylang trees

Ylang Ylang is typically grown from seeds, seeds older than 6months have Better germination than fresh seed.

Cuttings are iffy, I would try a 4-6" piece of semi-hard stem with 2-3 leaves max using strong root stimulant.