Read the show schedule carefully.  The rules for the shows differ from
society to society so make sure you understand the rules for the show you are entering
     It helps to highlight classes you plan to enter.  For disbudded HT,
Grandiflora, Floribunda or Polyantha class, remove all side buds.
For HT, Floribunda, or Grandiflora spray, remove the largest bud in the center to allow the side buds to create a pleasing "inflorescence", or arrangement of the flowers.
Water your garden generously days before the show.
"Freshness of bloom is key to winning", says Robert Martin Jr., author of Showing Good Roses.  Cutting blooms as close to show date as possible is best. Ideally, stem will be 22-26 inches long. This allows for any re-cutting to be done later.  Think proportion when cutting.  Blooms should be about 1/2 - 1/3 open.  Number of petals account for how fast or slow the bloom opens.
After cutting, immediately submerge the stem in water. Some exhibitors
recommend re-cutting under water. (I do this only if there's time to spare.)
Grooming:  Clean the foliage with a soft damp cloth. Remove all dirt and spray residue. Use a Q-tip to remove moisture on blooms.  Trim edges of damaged leaves. Long sepals (are distracting to the judges), and should be trimmed. Q-Tips may be use to adjust the arrangement of the petals, and work the center as needed. Use discretion when removing petals. Try to maintain the natural beauty of the rose. There is such a thing as "overgrooming".
On disbudded classes, make sure all side buds are removed. Do not leave any unsightly stubs where side buds have been removed.  Some exhibitors use an Exacto knife. I use a nail clipper, but it does not do as good a job.
Showing a Spray: At least two blooms is considered a spray. May include some buds, but blooms should be the major portion of the exhibit. Buds showing color preferred by judges. I remove green buds.
Open Bloom: Make sure the stamens are showing. Petaloids, or a few petals may be removed to expose the stamens. Excessive plucking will leave an
unnatural center that is distracting to the judges.
Fresh bright stamens are best.
OGRs: Again, read the schedule carefully. Know when the rose was introduced or if it Maybe shown stem on stem.
Staging:  Presenting your rose to the judges is very important. The stem should stand erect in the vase, and should be proportional to the size of the bloom. Wedging material such as saran wrap or foil may be used. They should not stick out beyond the mouth of the vase.
Filling Out Entry Tags:  Filling out entry tags in advance helps reduce stress on the day of the show.  Make sure top and bottom portions of the tag are filled out. Fill out all required elements. Omissions are grounds for disqualification as well as writing the incorrect name of the rose.
Placing the rose: Make sure your exhibit is labeled with the correct class, and placed in the correct place. Misplaced and misclassed roses are grounds for disqualification.
Grooming Kit: (From: Rose Exhibiting By Beginners, by Phylis Allen)
Some exhibitors use a metal or plastic case to hold grooming tools and other needs for the show: Q-Tips, tweezers, small, sharp scissors, small camel-hair brush, plastic wrap, labels with your name and address, and the ARS Handbook for Selecting Roses. If possible get entry tags ahead of time and put on the
labels.
     I bring a prunner for re-cutting stems when necessary. I also bring paper towels for cleaning up spills. And always tidy up your work area.