Well I like to look over the trailer about three days before the show. Clean it if it needs cleaning, tire check... etc...
For the horse the night before I give him or her a bath, bag up the tail, sheet him if its cool enough for a sheet.
I also the day before load up the trailer with everything I need (hay, tack, buckets ... etc). While taking the time looking things over to make sure they are not damaged and needing to be replaced.
I get everything ready so in the morning all I gotta do is load up and go