I still consider myself new to the BGS and I wanted to know if this character would work out okay: STR:18, DEX:18, CON:12, INT:18, WIS:12, CHR:12 Race: Half-elf, Multi-class cleric mage. One thing I want to know is what importance does wisdom and intelligence have and of course simply whether or not its a good build. Also I am playing this in the BGtrilogy with the unfinished business packs from the start of BG1. So far its good I am just worried about my few mage and cleric spell slots (one slot for each). I have played through the game all the way to the city of Baldurs Gate with a gnome illusionist with five others in tow and feel that my character is a little useless at times when none of my spells will help and my character just slingshots away while Minsc and Khalid are winning the fight which is why a made the new character.

personally i would suggest raising wis to 18 since it's the primary attribute for cleric and also if you intend on using wish (mage 9lvl spell) at later levels since it's success rate depends on wis if i remember correctly.

also str/dex 18 is a little over the top imo, in the end spellcasters aren't front line characters so why bother wasting stats on "fighting attributes", of course dex 18 gives you -4 in armor class which always helps but in the end it is not necessary, just keep your character in the background. (in higher levels certain spells make this somewhat irrelevant anyways since damage/hits can be blocked other ways)

on the other hand it might be useful to raise con to 18 to get bonus hit points since cleric/mage is pretty weak combo hp wise so it won't die on one arrow or something.

[url=http://playithardcore.com/pihwiki/index.php?title=Baldur's_Gate:_Races_and_Stats]here[/url] you can read on the differences of each attribute and what bonuses/effects they might have on your character depending on your class and such.

so for summary i'd use stats something like this:
con 18
int 18
wis 18
rest if you have rolled enough points (or if you feel like using certain stats regardless of rolls you can always edit the character via editor),
dex 18
str 10+
chr whatever you have left

of course there are items and equipment to boost your stats in different ways so there is some room for juggling with these.

well anyways this is my personal advice and i don't claim it to be the best advice and others might tell you to do differently, i guess in the end you have to do a little experimenting and figure out yourself what kind of character build to use but imo that is part of the fun, hope this helps ;)

Yeah, swap your points in STR and DEX for WIS and CON...

About stats:

Look at the stat tables in the manual, you'll often see that 14 isn't better than 7 and only extreme values make a difference.

18 str is nice is nice to have for comfortable carrying capacity and bonuses in melee if needed. If you need more stat points you could lower it to 10 or 12 instead.
18 dex is essential for the +4 AC bonus, the ranged attack bonus doesn't hurt.
12 con isn't better than 7 (just look at the stat tables) so you wasted 5 stat points for nothing. 16 con (you can start with 15 and read the book for additional +1) grants 2 extra hitpoints per level which will make a difference.
Int affects the maximum number of spells per level your mage can learn from scrolls, having to drink potions to raise it temporarily is annoying, so 18 is fine.
12 wis isn't better than 9 so you wasted 3 stat points, wis grants extra spells per day which is fun but you can do without, either take an high value or dump it.
12 charisma is pointless, you wouldn't even feel the difference if you had 8 instead. You could simply dump it to 3, you have a party member with high charisma which should be put on position 1 and do the talking.

Your new character won't be better than the old one. Physical combat is still pathetic, you'll have access to both cleric and mage spells but spell and casting level will be lower.
Gnome cleric/illusionist would have more spells because of the specialization bonuses.

If you want physical combat power you need warrior levels for weapon specialization.

Good mage/cleric build:

CON 16. Unless you're a fighter-type class, you get no bonus whatsoever even from CON 19 compared to 16. (At 20 CON you start to regenerate HP, although very slowly.) Your mage/cleric will only get +2 hp/level maximum.
DEX 18. Boosts your AC, helps with your sling when you're out of spells.
STR whatever. You won't be wearing armor (except for elven chain) if you want to cast spells, so you likely aren't going to be up front very often.
INT 18. Otherwise you're crippling your magery.
WIS 18. Otherwise you're crippling your priestiness.
CHA whatever. You can use Friends in BG1 and there's a ring in BG2 that makes this stat obsolete.

Str about 10 or max - raise with an item (or potion or spell) if you want to melee
Dex about 10 or max - raise with an item if you want a better armor class
Con 16 - you won't get a bonus for a higher con than 16
Int 18
Wis 18
Cha whatever score - can be raised with an item

Use STR as dump stat number 2 after CHA. DEX and CON is more important for survival, and as Cleric/Mage you want max WIS and INT.
You'll find items that give you STR 18(00) or higher, or you can use the long lasting Strength spell.

You should definitely max DEX, INT, WIS, and get CON to 16. If you can manage 18 STR that'd be cool, but I know 12 will let you use a number of weapons and at least Medium shields, and 15 will let you use most weapons and large shields. You could also use STR as a dump stat, build up your CHA instead and then give your character a strength enhancing item.

For a better understanding of Stats in BG, I recommend reading this:
[url=http://playithardcore.com/pihwiki/index.php?title=Baldur%27s_Gate:_Races_and_Stats]http://playithardcore.com/pihwiki/index.php?title=Baldur%27s_Gate:_Races_and_Stats[/url]

Thanks for all the reponses, the information I have now shows me how important it is to read the manual, to be honest I usually read everything in an RPG manual if its made of paper and I can hold it in my hands, my excuse for neglecting this habit is that the whole digital manual never really felt as fun to read. I will mark a solution as soon as I play and try the suggestions everyone has given.