so many variables..
If its a sprint trip..look for the muscular types.....shine in the coats are a good indication..and look for a horse with his head up ears pricked and not sweating up..
The longer trips looks for the longer legged horse...very relaxed ..nice scope to it and length of reign..

but best thing to do imo in these types of meetings is follow the good local trainer....and the horses trained on the track...
this is what i do when i'm at these types of meetings and usually to ****ed to venture out to the parading ring..
its all alittle vague but i think i usually do pretty well..

good luck ..