Hiya.
Old School Grognard DM here (30+ years of RPG'ing), and I play 1e AD&D, Basic D&D (BECMI;RC) and Hackmaster (4e and the new Basic). Anyway...
...I tend to change campaign to campaign, but overall my key thoughts are to give XP as listed in the book, flat bonus amounts for key game stuff (rolling a Critical hit, making a perfect skill check, etc), flat bonus amount for gaming-group stuff (making everyone laugh, keeping everyone focused, keeping good notes/maps from session to session, buying the pizza, etc.), and then I award a "next level %'age" for goals completed.
The "goals" bonuses tend to be Personal (character oriented), Minor, Major and Story. I give a flat % bonus equal to whatever their character needs for next level as a bonus. So, for example, a fighter needing 2000xp for 2nd level who completes a Minor goal might get a "5%" bonus; this would be 100xp. That same fighter who completes a Major goal might get a "10%" bonus (200xp), while the end of that Story bonus may be "20%" (or, 400xp). So, just on adventuring alone, no killing and whatnot, that 1st level character is going to have 700xp.
The 'goal' oriented approach allows for party cohesion, without the players feeling the must kill everything in sight. It actually becomes somewhat detrimental to do that, as it's more likely to get them hurt/killed, as well as alert their enemies, thus making them less likely to achieve certain goals...
For other games, I do tend to be a bit more 'fast and loose' with the xp, but try to keep it in line with my percieved tone of the game.
^_^
Paul L. Ming