With 8-ball, the most common way two people wager is by having what is called a "race". If both players are of similar skill and experience, you can start the race out at an even number such as a race to five games. Keep track of the games, and whoever wins five games first wins the bet. You can keep track of the score any way you like, but keep the score in a way that is clear and indisputable to all parties involved. Almost nothing causes more unnecessary drama in pool betting than inaccurate or questionable score keeping.

If the players have a gap in skill or experience, the "race" can easily be adjusted to make the more experienced player win more games to win the race. For example, the better player could play to win 7 games, and the less-experienced player only has to win 5 games to win the race. This would be called a "7-5 race for $20" or whatever amount you decide is fun.

In 9-ball, this same race format can be used, but due to the rotation nature of the game, you can also incorporate "spots" (balls needed to win individual games) into each game of a set. Normally, whoever makes the 9 wins the game, but a less-experienced player can be given a "spot" to make each game easier for them to win. A more experienced player can "give you the 8", and you would only have to shoot the balls in rotation up to making the 8 to win the game. The more experienced player would still have to make the 9 to win the game. You can adjust that "spot" as far as necessary to roughly balance the odds where a reasonable challenge is presented to both players despite the difference in experience or skill.

Lots of creative methods are used to balance the odds between two players, and by far the most important thing (regardless of what is arranged) is that whatever is arranged is completely and clearly understood by all parties participating in the gambling. Be clear and concise with the terms you seek, and make sure you get clear and concise agreement with your opponent before you begin the match. If one player is obviously dominating each set with a given spot, then the player who is easily winning should be open-minded about adjusting the spot to allow the matches to be more competitive. These are the standards of "gentleman pool", which I am a strong proponent of, although gambling in general can bring out the worst in people from time to time. Just do your best to promote a fair and balanced game, and be a gracious loser as well as a gracious winner and people will be happy they had the opportunity to play with you.