James Jacobs
Adventurer
Arbitrary level-ups when the GM says at the end of (or the middle of) an adventure are a good way to go with Adventure Paths. That said, make sure that your players know you're doing that. The accumulation of XP is more than just a tool to track your progress, after all... they're points you get for playing the game. They're rewards you get, and the feeling of building these points up is actually pretty satisfying and lets the players have a concrete scale they can look at to estimate when they'll be leveling up.
One thing I've done in the Savage Tide campaign I'm running is to simply hand out XP for the monsters and traps as normal, and I just keep an eye on what level PCs are. If they're falling behind, I start making up "story awards" for significant things they've accomplished in the session. If they're running ahead, I hand out less story awards. In this way, I've been able to keep the PCs at the levels they should be for each adventure and the players don't really know what is and isn't an ad-hoc experience award (even though I generally tell them everything they did that gets them XP to encourage them to do similar things in the future). This system works pretty well for me, especially since I've added in several bonus side adventures here and there and how much XP they need is a great gauge of how many encounters I need to send the party on. If I were just handing out levels when they needed them, I wouldn't be as able to send them on side adventures that have little to do with the Adventure Path's plot without that adventure seeming pointless to the PCs... since it would run the danger of artificially extending the amount of time between XP awards.
One thing I've done in the Savage Tide campaign I'm running is to simply hand out XP for the monsters and traps as normal, and I just keep an eye on what level PCs are. If they're falling behind, I start making up "story awards" for significant things they've accomplished in the session. If they're running ahead, I hand out less story awards. In this way, I've been able to keep the PCs at the levels they should be for each adventure and the players don't really know what is and isn't an ad-hoc experience award (even though I generally tell them everything they did that gets them XP to encourage them to do similar things in the future). This system works pretty well for me, especially since I've added in several bonus side adventures here and there and how much XP they need is a great gauge of how many encounters I need to send the party on. If I were just handing out levels when they needed them, I wouldn't be as able to send them on side adventures that have little to do with the Adventure Path's plot without that adventure seeming pointless to the PCs... since it would run the danger of artificially extending the amount of time between XP awards.