Each frog has speed and stamina statistics that are used to determine the winner of the race. Happiness is also a factor, as well as randomly occurring dragonflies on the course which will give the racer a speed boost. According to the developers, the only skill involved in the racing is to breed the fastest frog, with the only luck involved being the random boosts created by the dragonflies. Having a frog with the highest speed and stamina does not ensure a win, though; a frog with lower scores can still win, but will do so less often. It is suggested to use a frog with a much higher stamina than speed, which will allow the frog to hop more continuously and stop less often.
You can enter any frog into a race by selecting "Games" from the frog's page (the same page you would normally Breed or Sell the frog from), and then selecting "Race." A fee is charged for each entry into a race, slightly less then the cost of the max value of the frog. Only frogs with a rarity level at or below the player's level can play these games.
Coming in first allows you to choose either a certain amount in coin payoff or your choice of any other frog which competed against you. If your mailbox is full, you will automatically recieve the coins. Placing in second pays in a small profit while third results in a payoff of slightly less than the entry fee (but no frog selection for either), and placing in fourth or fifth results in a "Better luck next time!"
You can choose to leave the race early at any time, but it will automatically be considered a loss and no prizes will be given. You can only race frogs that have been tamed and are fully mature, while it was possible to race frogs that are not mature when this activity was first introduced in version 1.0.6, in version 1.0.7 and later only mature and tamed frogs can race.
Speed and Stamina
Each frog has an individual set of speed and stamina statistics that vary by the pattern/base color/pattern color combination. For example, a Maroon Tingo Anura has a speed of 6 and a stamina of 7, while a Maroon Carota Anura has a speed of 6 and a stamina 6.
The rarity of the the pattern indicates the speed and stamina range that is possible for any given color combination. This information is available when you select to view a frog (under their value), as well as in the Froggydex. The highest speed and stamina will be close to 7 times the level of the frog. Higher level frogs will be a point or two below: for example, the best level 10 frog has 68 not 70 for speed and stamina. The Racing Value Database has the speed and stamina for most frogs.
Frogs will always race against four other computer-run frogs at the same rarity level, so only the speed and stamina relative to that rarity determine the frog's racing prowess. You will not be racing your Anura against Stellata frogs because the award for the winning frog includes selecting one of the other frogs as a prize. This is a good way to get the rest of the patterns at a certain rarity level once you have one of the patterns -- as long as your one frog is a good racer, of course.
Stamina determines how quickly the frog loses happiness level, while speed determines how quickly the frog will hop along the race. During the course of a race, the happiness level of the frog decreases as he hops along. For each dragonfly eaten, some happiness is regained (similar to the amount gained in pond hopping); also, a potion can be administered once at any time during the race to return the frog's happiness to 100%. The happier the frog, the faster the frog will hop along. If the frog's happiness reaches 0%, it will still hop, but at a very slow pace.
One strategy is to choose a frog with higher stamina than speed: a bigger difference lets the frog hop more continuously.