I am ready to go to Spellhold is there anything I should do,bring or get before I go??? Which NPC's are best to have there....Thanks

Take the NPCs you want to have in your final party - you'll be away for a while and you get a lot of experience. If you're going to add Imoen, bring equipment for her and spells for her to put in her spellbook. And if you're going to get Imoen, don't bring an NPC that you'll swap her for that you might want to add to your party again later - you won't be able to get them back. Don't worry too much about stocking up on arrows etc, you can buy them there.

If your comfortable with your current party, go with it. BG2 can be beaten with any type of party, and even without a party.

I would bring Gem bags and Scroll cases, and stock up on Extra Healing potions.

This is kind of stupid advice, but I wish I had gotten it. Save practically every 30 seconds! After every battle that you are sure all enemies are dead, save! Trust me, I went easily through many parts, only to blindly stumble into a heavily guarded room, and spend much time getting back, which was tiresome. Have Fun in the asylum!
-Brainless One

Don't bring gem bags, I'm pretty sure you can find them in Spell Hold. But bring a bag of holding.
Take Yoshimo with you.

Wait. Bring a bag of holding? Isnt spellhold where you find the bag of holding? My memory must be playing tricks on me, or Im right. Either way is bad.
-Brainless One

I'm sure you can find a gem bag, not sure about a bag of holding. Either way, bring one with you.

I never found a Gembag in Spellhold...past Spellhold I found a few though.

You find the the Bag of Holding in Spellhold, after Bodhi releases you into the 'maze'

thanks all

You are welcome, sorry for getting off track with the bag thing.
-Brainless One