You can always use a few extra rags with your grooming supplies, and of course don't forget your show clothes and your show tack. If you have an extra halter, lead rope, bridle and girth these are the things most likely to break on you so throw them in. You may also enjoy a change of clothes for the ride home.
It is nice to have a muck bucket and manure fork to clean out the trailer and clean up the area where the horse will be tied or stabled during the day. Not only will it keep your horse's legs clean, your boots clean, and smell better, but it will also keep the flies down.
Last but not least, don't forget your rain gear. Hopefully you won't need it, but most shows go on, rain or shine, unless it is a complete washout with dangerous lightning.
Have Fun!
