I just reached the maximum amount of spells I can learn for level 6 spells. Now I found a really cool new one but cant learn it. I heard there is a way of forgetting learned spells? How does this work?

You can just simply click on the spell you want to forget, then an option comes up if you really want to delete it. Then you can remember another spell in exchange for the one you forget

Actually I meant completely deleting a spell from your spellbook. Sorry if I was unclear about that.

right click on the spell in the spell book; no the memorised ones the otehr one; then u can select to delete it,.

Nooo! Completely WRONG! The number of spells which you can learn at a particular spell level depends on your INT. If you run out of "free space" for the spells then you have to increase your INT. You can do it by means of potions. Therefore:
a) Collect spells which you cannot learn with your current INT.
b) Drink some kind of potion of genius.
c) Learn the spells.
Once you have learned the spells, your INT can decrease. The spells will not vanish. You will have more spells in your spellbook that you should have. That's all.

Radek, ofcourse, why didnt I think of that, its so simple. Thanks a bunch!!! And ofcourse Jaegan and Calaethis Dragonsbane thanks as well for your input.

I believe that you can completely forget and wipe spells of of your spell book in ToB. Too bad I don't have it. :(

You can also wait till next lvl then learn more that way.

Actually, that "forgetting spells" trick is a rather cheesy way of getting a bunch of XP. Get a bunch of spell scrolls (pickpocket or purchase). Then memorize them, delete them from your spell book, and memorize them again. Since BG2 gives XP for successfully memorizing spells, your XP keeps increasing. ;)

Cheers,
-Sazerac