Pangaea666: I'm playing BG2 right now for the first time, and "easy" isn't exactly a word I would use to describe it ;) Space bar is very important though. Set it to auto-pause, at least for traps found and enemies sighted. Have started using it for spells cast too, and of course NPCs injured (30% health left). This isn't a hack and slash, so you need to think about what to do, and for that you need liberal use of the spacebar. Probably best to play BG1 first if you haven't tried it, because then you'll understand the basics better and learn what low-level spells are good. The very basics, however, is that you want low Thac0 and low AC. You don't need to know about the details about hit dice and all that jazz, I don't understand all the small details either. As long as you try to get low AC and low Thac0, you're good. And both will lower with better equipment and with more level upgrades. If you're starting right on BG2, mages and priests is where the action is, and their spell libraries is quite a mouthful. So I actually recommend playing BG1 first, through easyTutu so the game looks and performs much better. That way you both learn the gameplay better, and get the story from the beginning. For BG1 especially, keep in mind that Ranged Weapons is King.
In BG2 the spellcasters are much more dreadful than their counterparts in BG1. You probably noticed that most of them cast protection spells on themselves as soon as they saw the player. Some of the common protection spells are: Stoneskin, Mislead, Mirror Image, Protection from normal weapons/missiles, etc. and many advanced spellcasters use Spell Shield, Contigency as well as Spell Deflection, etc.
Now, if you ever want to touch him, you have to disable some of the defenses. You can look at the description pages in the manual for a basic idea about what each spell does, but here are some ideas: First you need to deplete his Spell Absortion (some spells absorb certain levels of magic or certain numbers of magic); Next you need to use "Oracle" to disable all illusions; And you also need to cast Dispel Magic, Breach to further bring down his magical defenses. Now that you have access for better spells later, but Breach probably is going to stay with you for a long time (Breach is lvl6 which means you have to be lvl11 to cast it). If you have Keldorn, his Dispel Magic is much more powerful than yours, as he is an Inquisitor and if my memory does not fail me his level is doubled on calculation of Dispel Magic, better is that he casts faster than you.
After you bring down his defenses, you must be aware of his magical attacks. Protect your team from Mind-Influence spells, which are the most annoying. Some equipment can help, as well as some potions, and some spells of course. He will also try to bring down your magical defense, but as long as your fighters and archers can "muscle " him, there should be no trouble after a few rounds. And of course, cast Haste/Resist Fear/Bless/Mirror Image/etc. on your team and drink some potions before the fight.