factors to consider when evaluating a hobby:

the cost of the hobby
- flying planes, sailing boats, and riding horses are expensive hobbies. soccer, skateboarding, and yoga are relatively cheap. aside from equipment, you should also consider other costs, like transportation and medical costs: e.g. having to drive 40 miles to go swing dancing is an added cost; breaking bones as a snowboarder is an added cost.

- it may be better to choose cheap hobbies that produce thrills rather than expensive hobbies that produce thrills. ex: I recently heard an ex-helicopter pilot say that he prefers powered-paragliding to flying a blackhawk, which was the complete opposite of what I would have expected (it really caught me off-guard). it made me remember that driving a car on the highway was a huge rush the first few times i did it, but soon became routine. the same pattern seems likely to show up with flying a plane/helicopter, but those will cost me a lot of money per moment of excitement. so it may be better to do something cheap that also produces thrills (e.g. stand-up comedy or acting). i haven't made up my mind, yet, though.

the excitement from the hobby
- excitement can come from acceleration (cars), fear of pain (skateboarding), other in-born fears (climbing/fear of heights), strenuous effort combined with competition (soccer). more excitement seems to often make for a more enjoyable hobby. the big trade-off seems to be with danger; more excitement can often mean more danger. [connection: in "the 4-hour workweek" the author talks about how you should primarily seek excitement in your life]

the number of people near you who do the hobby
- people feel better after interacting with other people, and hobbies are a good way to get that interaction. but if no one around you shares your hobby, you won't enjoy that benefit and may want to consider adopting a second hobby.

the likelihood that you'll become the best at the hobby
- hobbies tend to be more enjoyable when you're the best at them among those you hang out with, because the other people who have that hobby will tend to treat you well.

the culture of the hobby
- if your hobby involves getting together with other people, pick a hobby that will bring you together with people you will enjoy spending time with. for example, rapping tends to have a particular culture even though that culture is not essential to the actual skills they use (e.g. weird al's "white and nerdy" is a great rap song). if you're an asian baptist who wants to start a death metal bible band, you may have trouble finding a crowd to practice your hobby with.

the skills you're developing from the hobby
- animals play around to practice skills they'll need later in life (like how to fight). bill gates played monopoly and risk as a kid and his family held competitive team events; presumably this gave him some great experience with cutting deals, being aggressive, and working as part of a team.

- even hobbies that may seem useless to many people can serve as valuable analogies for analyzing other aspects of your life
example 1: for a time in high school i played a computer role-playing-game called Diablo 2 in which you control a character who fights demons and gradually learns different fighting skills. the majority of your time playing the game involves clicking furiously on monsters to kill them; in hindsight the game seems pretty repetitive, but I gained a valuable insight into the relationship between your time and your skills: the game was set up so that you couldn't learn every skill to the maximum degree possible; in fact, you could only fully develop a small subset of the abilities open to you. if you developed your skills in an inefficient manner (e.g. partially developing every possible skill, including those you wouldn't likely use as much), you wouldn't have as powerful a character as some other player who chose to develop their skills in a more thought-out manner (fully developing several skills, and only developing those skills that they would be using). to bring the analogy back: most people spend their lives dabbling in many different hobbies, jobs, and interests, and so they never really excel in any one area. the guys who get all the attention are the ones who've been dedicated solely to a single pursuit for a long time (mozart, tiger woods, michael jackson, warren buffet, etc). of course, the question remains: is it better to have that recognition or is it better to experience the variety of many different pursuits? I'm honestly not sure yet what the answer to that is, but at the very least it seems worth being aware of this trade-off. One of the reasons I stopped playing videogames is that I noticed that I wasn't really making any cumulative gains: I would become proficient at one game, but when that game went out of style all of those hours I had spent learning to play it seemed suddenly useless (or at least less useful). I didn't like that.
example 2: Mark Cuban was an avid stamp collector as a teenager and learned a lot of useful business skills from his hobby. he has a post about that I need to track down.