You got the strips? All you gotta do is water until some comes out the bottom of the pot, Collect that into a beaker(or anything that holds water), And dip your strip.
I usually use the reagent one. but then I need exactly 5ml of water or my test starts going off. I stole a dropper off a baby aspirin bottle. It has up to 1ml marked.
Tobacco smoke will kill your plant. Nicotine will keep bugs away but the tar will coat and suffocate the leaves. Best to keep the cigs away. Like stinky says, let it dry out completely before watering again.
I have waited to water too long before, All that happened was droopy looking weak plants, After a good watering, They sprung back up within hours.