Your local fish store or even petsmart should ba able to direct you to a test kit for your basic water parameters - I suggest you get the aquarium pharmiceutical's freshwater master test kit (shouldn't be much more than $30). The test kit should have instructions on how to test the water - I know for sure that the aquarium pharmicueticals test kit(s) have writen and picture-by-picture instructions.
A basic run down on the parameter's you should be conserned about:
Ammonia - this will burn the fishes gills, to varying degrees, sometimes doing permanenet damage. Keep it at ZERO or VERY close to it via doing water changes if and when nessisary of the percentage ammonia needs to be lowered by (although you need to leave enough water in the tank for the fish to stay submerged, of course).
NitrIte - This prevents oxygen uptake into the blood. Keep it at or VERY close to ZERO using the same method I described for ammonia above. The capital I in the title is used so you and I don't confuse this with nitrAte. Short term use of aquarium salt can help here, although I would strongly advise against relying on this to keep your fish safe.
NitrAte - This is non-toxic, although it is a good indicater of
Dissolved
Organic
Compounds, wich are toxic. DOC's are not tested for becuase they are hard for the average home aquarist to test for, becuase you need labratory grade testing equipment to do so. Keep the nitrAte under 20 via doing your weekly water changes - do larger (and possibly more frequent) water chamges if nitrAtes are higher than 20 at the end of the week, do less if you want if the nitrAte is lower than 20 at the end of the week. If you have growing live plants, they will remove nitrAte and give you a lower than actual indication of DOC's so for my planted tanks, I just do (and I suggest you do to) 50% water changes once a week.
Now that, you've probably got a grasp of what the water parameter's are, I suggest you read this article:
http://www.aquariumboard.com/forums/articles/26-cycling-tank-fw.html so you can understand how all this stuff stays in the right numbers in established tanks, and how to get your tank to that point where ammonia and nirtIte will stay at zero on it's own.