A Random Babble About Barbarians:
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Barbarians are different in design to Fighters, but they are mostly similar. Concepts that apply to Fighters, usually apply to Barbarians as well, and vice-versa. Both of them are Warriors, and though Warriors are generally one of the easiest class to play with, it does not hurt to do some pre-planning as well.
The following is not strict roleplaying( as it takes advantage of hindsight), but I do believe it does allow for a certain degree of roleplaying, even though some purists may scream that it is actually rollplaying. I leave it to the reader to decide what it actually is.
Optimal Stats:
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STR: 18/~~
Not much explanation needed here, as STR is one of the key statistics for a Warrior class. It improves your THACO and your damage, not to mention increasing your inventory weight capacity.
DEX: 18
Another no-brainer as 18 here will give you a -4 AC bonus. Less hits are always welcome.
CON: 18
More CON means more HP. Barbarians gain a huge advantage in the HP department as they roll 1d12s for their initial 9 levels. To ensure that you get the maximum amount of HP each time you level up, tone down the difficulty to Normal before you level up, then change it back to the original difficulty.
WIS: 10
Technically you can lower it even more, but 10 is the minimum if you do not want any Lore penalties. If you want to disregard Lore totally and assume that your Barbarian is a gullible naive twit( which sadly, the PC is doomed to be anyway...), lower it further by all means.
INT: 10
Again, 9 is technically the minimum so that you can use the Green Protection Scrolls, but 10 is where you will receive no Lore penalties.
CHA: 08
Yee be a stinking Barbarian.

Jesting aside, 8 is a nice round number and incurs no reaction penalties from other people. It makes you neutral in appearance to put it one way, ignoring reputation.
This makes a total roll of 82 points. Very easily gotten.
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Barbarians are immuned to backstabs. I cannot emphasise how amusing it is to see Twisted Rune Assassins wave their short swords helplessly as their bladed weapons poke your character before getting their skulls smashed in. This ability makes some of the quests in the game amusingly easy, whereas other classes would find it daunting.
One quest in particular, seems to be tailored-made for a Barbarian. It is found in the Bridge District, and by the way, Barbarian Rage confers immunity to Hold( among other benefits), which also makes it useful in this encounter.
Speaking of which... remember those pesky Vampires? Especially those that ambush you at night? Consider them free XP now because, Ding-ding-ding! Barbarian Rage confers, you guessed it, immunity to Level-Drain! Due to this immunity, you render them as nothing more than over-sized mosquitoes worth 8000+ XP.
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You start off with 6*. If you really want a powerhouse, Flails and Warhammers are really the way to go. Sword and Shield Style is utterly useless, rendered pointless by the presence of two shields in Ribald's store,
The Fortress Shield
The Shield of Reflection
Personally, I would put 3* in Two Weapon Style, 2* in Long Swords, and 1* in Flails at the start. The next * at level 9 maxes out the Flails.
The Flail of Ages should be retrieved ASAP, but try to buy the Girdle of Hill Giant Strength first, before setting out to the De'Arnise Keep. Note that you do not need to complete the quest to build the Flail of Ages, unless you have the Improved Torgal mod.
If you have the Bonus Merchants, get the Defender of Easthaven from Joluv in the Copper Coronet and place it in the off-hand. Keep it shiny, it is truly a lovely weapon. Other Flails to look out for include the Sleeper that Bernard sells. Not necessarily one of the most powerful weapons in the game, but it is deceptively potent.
You will want some +4 enchanted weapons though, and this is where Long Swords will come in. Do the Tradesmeet quest and if you play your cards carefully, you will get Flame Tongue. Failing that, you can always consider pumping points into Halberds and get Dragonsbane from the Cult of the Unseeing Quest, then upgrade to Dragon's Breath from the Underdark, and finally the Ravager from ToB.
Quarterstaffs are another viable option, with the Staff of Rynn +4 from Ribald, later to be switched with the Staff of the Ram in ToB. Just remember that to maximise your potential with 2-Handed Weapons, maximise your Two-Handed Weapon Style.
For Warhammers, the Giantkin Warhammer is +4 enchanted despite its' low damage, to be upgraded to Crom Faeyr in Chapter 6.
I suppose I could say more, but I am not the Barbarian expert around here. I dare say that would be Jim instead.