When reading forums devoted to D&D, I often hear players and gamemasters complaining about experience points. Sometimes it's that they are a pain to calculate (especially in later editions of D&D). Other times it is that they seem very biased toward combat as the only way to earn "enough" experience points. I replaced the standard experience point system in many of my D&D/AD&D games in the 1980s with a very simple, activity neutral "adventure point" system. Adventure points are given out in much smaller numbers than experience points and are given out to characters for mainly for participating actively and contributing to the session in accordance with their abilities.
The first thing you need to do to use adventure points is to decide how many game sessions, on average, you want it to take for characters to advance a level. Let's say you want it to take 5 sessions and you usually play for about 4 hours a session. 5 times 4 is 20, so you have a base of 20 adventure points to go up a level. For each hour or part thereof a character participates in play to the extent the situation allows, the character earns one adventure point. When he has 20, he can spend them to advance a level.
Of course, you can make things a bit more interesting with special AP award categories. For each such award category you want, you add an extra hour to session length for the purpose of determine the number of adventure points needed to advance a level. For example, you might want to have two special AP award categories: one for playing in character (or within one's class/niche) and another working well with other characters. This would add 2 to the number of hours in an average session for the purpose of determining the number of number of adventure points needed to advance. Continuing with the example above, 5 times 6 is 30 so with two special AP award categories, 30 adventure points would be needed to advance to the next level.
Awarding points in special award categories is easy. If the character did average in the category, she gets one adventure point for the award category for the session. If the character did well below average, he gets no adventure points for the award category for the session. A character who does well above average for the seesion earns two adventure points for the award category for the session. The default is average, give the character a point.
You can also give an overall bonus point or two to everyone if the session was more fun that usual, accomplished some major campaign goal, or the like.
Some versions of D&D have experience point advancement requirements that vary by class. You can simulate this with adventure points by have a different amount of adventure points required to advance a level for each class. An easy way to do this is to come up with an adventure point total based on the above system. Then use 110% (round up) of it for classes that require more experience points than average to advance and 90% (round down) of it for classes that require fewer experience points than average to advance.
The main advantage of the adventure point system is that it is a heck of a lot less effort for both players and gamemasters. There are also a couple of important secondary benefits:
1) Successful adventuring is no longer mainly defined as defeating monsters in combat. You can get just as much advancement effect from avoiding the monsters, bargaining with them, intimidating them, fighting them just enough to make them run away, etc. Also time spend in non-combat activities is just as helpful to character advancement as time spent in combat.
2) It is much easier to have mixed level parties as the opposition can be targeted to the party without have to worry about giving the higher level characters less experience points than they need due to less challenging opposition.
This adventure point system is simple, but it can easily be made more complex if you want a bit more rule crunch.