David,
while the tank is cylcling its going to take some time for everything to get itself strightend out in there. sometimes a week, sometimes 6 weeks, ive even ehard of a number of months. You NEED a test kit that does ammonia, nitrites and nitrates at the very least. this will let you monitor how your cycle is going. it will start with high ammonia and probably little to no nitrites or nitrates and then the bacteria that eats ammonia will eventually get the job done and turn the ammonia into nitrites, then the same thing basically happens and the nitrites get turned into nitrates. once your ammonia is at 0 and your nitirites are at 0 and you have some nitrates left you can do a good sized water change of about 30% to reduce the ammount of nitrates in the water. There are bacterias you can add to the tank to speed up the cycle, but like the otehr poster said its better to just let it run its course. this is a thing of nature you are trying to recreate so its best to let nature run its course. ammonia and nitiriets are very toxic to fish, so don't get over anxiuos about adding anything untill they are gone. crabs and other inverts are harmed by nitrites and nitrates so you wont really be able to have a cleaning crew if you are going that direction until the cycle is done either. Once you get your nitrates to below 20 (you are shooting for as close to 0 as possible) then you can add the damsel or whatever you said you wanted to try.
The other poster asked if you live rock was cured meaning it sat in your tank or the local fish stores tank after getting seeded with the things that make live rock live. this takes a few weeks as well. once the rock is good to go then it goes in your tank and you will need a small power head to push water around in your tank to force water through the live rock. Live rock is one of the best filters you can get and you should probably have about 10 lbs of it in your tank. so the water pushes all the junk in your water into the live rock and the organisms in the rock eat it and break it down into other things that are less harmfull to your system.
Keep in mind that small tanks are harder to work with than large tanks because of the amount of water there. for example if you were to pour a can of pepsi into the ocean there is so much water there that it probably wouldnt hurt anyting except the plankton that it touched. if you poured a can of pepsi into a 500 gallon aquarium there is still a good amount of water there but not enough to jsut dispose of the bad stuff in the pepsi, that tank would need some emergeny help to keep things going, but if you poured a can of pepsi into your 10 gallon it would probably be over before you knew it and would kill everything in it quickly. Probably a poor analogy, but was the best i could come up with. so when something goes wrong in a small tank you need to be right on top of it and get it fixed quick before whatever is wrong kills your livestock.
Also with a smaller tank be sure and check your fish before you buy them as alot of fish need at least 55 gallons and some even need 100+ gallons to survive. You will probably be good with some smaller fish like clowns. and don't overfill your tank with fish.
Once your tank is cycled do a 10% water change with purified water every other week or at the very least once a month. If you dont have a water purifier (RO/DI reverse osmosis) system then you will need to either buy one or get your water from a fish store by the gallon. I would highly reccomend against using tap water as there are just to many things to go wrong
GL
