GAIN

Whenever you have accumulated the experience points needed to get your next level, you must go to your guildmaster and GAIN. This will advance you to your next level, give you your hit points, build points, and modify your abilities (such as THAC0 or backstab multiplier).

Again, you do NOT automatically gain a level when you get enough experience points -- you must find your guildmaster and talk to him to gain. As you get higher in level, the lower level guildmasters will be unable to teach you anymore and you must find more wiser guildmasters. These higher level guildmasters are often harder to find so you should always keep an eye out for them as you travel.