Have a look at this recent topic
http://www.champdogsforum.co.uk/cgi-bin/board/topic_show.pl?pid=746287;hl=matetel;hlm=and#pid746287I bought the matetel after using Premates without success the first time, not saying they don't work though ;-) I must admit I found getting enough saliva a real problem

but I think I managed to get the day of mating right. Basically you are looking for simple bubbles and line patterns when they are not ovulating, as they start to ovulate you look for "fern" patterns, once they have ovulated the ferns look like they are covered in ice or like a fingerprint...no bubbles. If you do a google search for "ferning & saliva" you should find some images, that might help you.
Never used a microscope but I would imagine you swipe the slide across the tongue and then let dry.