How do I handicap a horse race?

The term handicap derives from hand-in-cap, a popular seventeenth-century lottery game, where players placed their bets in a cap. Handicapping is used in scoring many games and competitive sports, including Go, chess, golf, bowling, polo, yacht racing, and track and field events. It also serves to foster wagering on horse racing events. Often, races, contests or tournaments where this practice is competitively employed are known as Handicaps.