The day itself
Arrive early so you have time to walk your dog, get settled and check in. Trials involve a lot of waiting, so plan a calm base for your dog. A covered crate in a quiet corner of your car or the building can help. Let your dog sniff and rest, and keep your own energy low.
When it is your turn, a steward or judge will explain the area and what to do. You will bring your dog in on leash, begin the search on cue, and tell the judge when you think your dog has found the hide. Judges are neutral, and most trial people are kind to new handlers.
Mistakes happen. You might call alert in the wrong spot, run out of time or have a dog who needs a break. In many sports this counts as a fault or a non-qualifying run, but it does not mean your dog failed. Take the information home and train from it. Never punish your dog for a bad run.
How a search is judged, in general
The judge watches your dog, not you, and decides whether your call is correct. Searches are timed. Rules cover where you can stand, how you can hold the leash, how you call the find, and what counts as a fault. They also cover what happens if your dog has an accident or needs to leave the area. These details change, so read the current rulebook and the trial rules before you go.
Handlers can only call a find when they believe the dog has located the source, so the key skill is reading your dog. See reading your dog on odor. Practice with a friend who sets blind hides and watches you call them. Aim for confidence, not speed.