When I was younger, I took for granted the sheer amount of free time I had. With a lot of this time (especially during my high school years), a lot of this time was devoted to gaming. As I got older, an increasing amount of responsibility and commitments meant less 'game time'. A few years ago, it meant next to no time spent on these sorts of pastimes.
As an adult who works a 40 hour workweek and who may have commitments which may include childcare or other necessary duties, it's easy to lose these little luxuries as other things become priorities. Add to that other friends who shared some of these hobbies who also have similar responsibilities or commitments and you may end up in a situation where games and game books collect dust on the shelves.
A few years ago, I managed to re-enter a hobby that I hadn't been a part of for a few years. Being a player is easy enough and the only requirement is devoting a bit of time on a regular basis. This could be once a week or even once every second week. However, the key here is to MAKE the time in order to get this to work. Sure, it won't always work and sometimes life will invariably demand your attention elsewhere. Gaming is a diversion but it shouldn't be used as a replacement. It's not hard to make a commitment and it shouldn't be too difficult to keep it.
If you think you are too busy to game, the first thing to do is to take a good look at your average week. See if there is a spot where you don't seem to do much or don't have something planned. If you do, how much time do you have to spare? Depending on what you do or play, you'll probably need 3 hours or so at a minimum. If you have more time available, then that's even better. However, it's better to game a solid 3 hours a week than none at all. If you can make that commitment on a regular basis, then you could be on your way to gaming regularly.
Aside from that, as a player, you don't necessarily have to worry about much else but participating. If something happens and you can't make a particular session, let your GM know as soon as you can. See what sort of requirements they need for an ongoing campaign? Do they have someone else play the character while you are absent or is the character taken out for play for that session.
If you can't do face to face, consider trying a game over the internet using Skype and other computer gaming aids. You can save a lot of time and get in and out of a game pretty quick if all you need to do is log into your computer. It is also a great way for friends to play over great distances and, even if everyone is local, is a way to avoid travel time.
Now, what if you are short on time but you want to actually run something yourself? This can be done as long as you keep a few things in mind. First keep it simple... play a game that is rules-light and don't get wrapped up in trying to design an enticing locales and NPC's before the fact. Consider published material for your adventures or take something you like and tweak it to suit your needs more. Do not create more work for yourself than what is needed.
When I stumbled upon C&C, this is the approach I took. I didn't worry about trying to create my own fantasy world or even overly develop my own adventures. I grabbed a handful of adventures which we played through and basically considered them as 'episodes'. Key things or questions which become a focus for the players and their characters in one adventure might create a hook or different angle for the new one. This will add to a more uniform feel to a series of adventures that were not originally linked as long as you allow it to develop naturally. Players have wonderful imaginations and all they need is a bit of inspiration for it to take off. In this way, the players help color the adventures you are putting them through and there is nothing wrong with taking advantage of that. Sometimes a great twist will be result of an action that a character makes or an idea that the player is trying to follow through on. Use it and enjoy gaming in the moment and it may go a long way to help reduce time to prepare for a gaming session.
Another idea is rotating the GM responsibilities if the group is generally limited when it comes to time. This doesn't work for everyone but some groups have had some success at sharing some of these responsibilities.
Of course, as I mentioned before, there are times when schedules conflict and nothing can be done to get out of certain plans. For me, April is proving to be a busy month. I'm currently involved in a BASH game that plays every two weeks and I was looking forward to playing a game of Victorious (currently in development) over Skype this Thursday. Circumstances have forced me to advise fellow players that I won't be participating in either game. That said, I have one C&C session I am running later this month but I will still try and get some general gaming here and there with a couple of friends between now and May.
It's important to make to make a bit of time and put in a bit of effort for the things you enjoy when you are able to. Seize the opportunity when you can and may your dice keep on rolling.