Tom Brohamer said that there is no better opportunuty than an early horse with the best second fraction. I believe he is right, because I have seen so many horses spit out a fast first fraction, only to quit right after that initial burst.
The reality is that almost any horse can spit out a fast first fraction. In my own wagering "adventures", I now look for the lone early horse in any dirt race. One thing I keep in mind is that if a horse is gonna be challenged at the first call, it is very unlikely that this horse will actually win the race.