Make sure this is filled out and sent in. It doesn't hurt to call ahead and find out what type of stabling is being offered if you are not familar with where you are going, that way you can specify special instructions on your stable card. For example, you can specify NOT to be stabled by a door, or you may request a Stallion end stall. Some local, and all out of state, shows require a negative coggins test. The shows takes copies so never give away your original.
Many shows also require a vet certificate verifying shots, so have that on hand as well.
Here are some tips that may help you avoid a frustrating situation. If you do not belong and you join prior to a show you simply put pending under the membership number on your entry form. If you do not belong you will be required to pay a non-member fee at every show you attend. If you belong to a local club you can usually obtain a reduced membership fee with these organizations. The same holds true with USDF - United States Dressage Federation, of which you MUST be a member for all sanctioned Dressage competitions.