Ground conditions should always be a factor in a punters decision making. There are a number of reasons why certain horses perform better on certain ground types. Smaller framed horses with low skimming running actions are typically more at home on firmer ground surfaces, whereas bigger horses, with high knee and stomping actions can find running on firm ground painful; but come into their own when the ground is heavy and the mud is flying. Finding a horse that's about to run in ideal underfoot conditions is always advised.
The expression 'Horses for Courses' is commonly used amongst punters and it shouldn't be ignored lightly. Racecourses differ immensely from one to the next, they can be right handed, left handed, tight, open, flat, undulating; so it's little surprise that certain types of horses fare better at certain types of tracks. When faced with the challenges of a specific course, it could be wise to back a horse who has fared well against them in the past.
Just like humans, some horses are built for speed, and others for stamina. A horse packed with endurance that's running in a short distance race is unlikely to be playing to its strengths, likewise, a speedster will not last out to the finish over a race distance that's too far. . You may be able to spot these horses in the race who will not be suited by the distance, quickly exclude these and back a better horse from the remaining list of more likely contenders. If you choose to back a horse that's running at its optimum race distance then you won't go far wrong.