two words
post position
you need to check the past results to see where they broke in their prior races, some dogs hate running on the inside, some on the outside. Usually outside is a big disadvantage because I don't think dogs understand the shortest distance around the track is on the inside (great insight huh?) . But even on the inside, depending on where they break, they can get wiped out and have no chance. Sometime you can get good prices on a dog that shows bad previous form but has been in trouble and gets a positive post position switch
Other advice - check the past results to see if inside is playing good, or if favorites are hitting - I'm not sure on dogs, but I know horse race favorites only hit about a third of the time, although in any short period it could be a lot higher or lower. If there is some big promotion at the track and a lot of 'casual fans' are there that could effect the betting also.
As far as crapping on the track, in horses that is a BAD sign - dogs not sure about what good body language for a dog is