[Note: The following rules are optional additions for campaign play.]
Player Characters will gain additional Experience at the end of each battle in which all enemies fled or were reduced to 0 Hit Points. The amount gained by each character will be equal to 【5 minus the number of rounds elapsed during the battle 】; this means that any battle concluded during the sixth round will grant no additional Experience, while a battle that was completed during the first round will award five XP to each participant.
It's good if: You like your battles to be intensely tactical, and you're okay with your campaign mostly revolving around combat. If you choose this optional rule, the Game Master will have to spend some more time making sure each encounter is challenging but also allows for clever strategies.
Each Player Character will automatically gain a level at the end of each session (in addition to normal advancement).
It's good if: Your campaign will be relatively short, if the Players like to have plenty of new tricks every session, and if you don't mind turning your game into a quickly escalating spiral of mayhem.
Depending on the campaign, you might want to use one or more of the optional rules. You can also introduce new advancement rules halfway through the campaign, or stop using them if you realize they are doing more harm than good.
What's important for you to understand is that the optional XP rules you apply will inevitably shift the focus of your game: after all, people generally tend to do what they're rewarded for.