The most important skill a handicapper can acquire is the capacity to determine which horse or horses will set or force the early pace of a race because horses that get or stalk the lead at the first call win far more than their fair share of races. There are professional handicappers who make their living using this one handicapping factor alone. Not only do such horses win more than their fair share of races, they always have an impact on the outcome of an event, regardless of the distance involved.
Many pace handicappers tend to focus on the internal fractional times of a horse rather than how close to the leader the animal was at each call. I believe this to be a mistake as horses are creatures of habit. Just because a horse ran the first quarter of a six furlong race in 22 1/5 seconds while chasing a pack of $16,000 claimers, does not mean the horse will run the same time in a race with $10,000 claimers. A horse that tends to run three to five lengths behind the pace setter at the first call will likely do so whether the timer is tripped by the lead horse in 22 1/5 or 23 1/5. Some horses have an inherent need to lead, some some are prone to stalk the leaders, and some like to come from far off the pace. The internal fractions of a race are the result of the makeup of that event; that particular set of horses.
Despite that, determining which horse is the speed of the race would appear to be the logical first step to handicapping a race. If you can determine ahead of time which horse is likely to set the pace, you can then move on to finding which horses tend to chase the pace, and which horses like to come from far off the lead. You will have found the key as to how the event will likely unfold.