Monday Night AD&D Campaign
Characters earn experience points (XP) by defeating enemies and acquiring treasure. Players earn bonus XP for their characters by showing up to the game sessions.
Regarding these points, note that non-combatants and helpless creatures are not considered enemies; XP are awarded on a 1 XP per 1 gp basis for treasure (not equipment) liberated from monsters, but no XP are gained from normal commerce; the bonus XP for attendance is a flat award, and is NOT modified if the character has a high score in their prime attribute.
When a character has enough XP to level up, they need to train to advance to the next level. Training costs either 1 week plus tuition fees (usually 500 gp per level of the instructor) or 2 weeks and practice materials costing 100 gp per (current) character level. If another character is willing to provide free tuition, the whole ordeal costs the minimum time and cost (1 week + 100 gp/character level). NOTE: Characters providing tuition must themselves have attained the level being trained.
Interested parties can compare these times and costs to those laid down in the AD&D Dungeon Master’s Guide, page 86.