When you level up you can distribute 5 points in strength, magic, dexterity or vitality. (Or divide the points of course.) After telling what each of these four do for a warrior, you can find how I distribute those points when playing with a warrior.
DEXTERITY
Dexterity not only increases your chance to hit (each 2 points in dex increases your chance to hit with 1) it also increases your Armor class (each 5 points in dex increases your AC with 1) and it increases your chance to block an attack. The higher your AC, the less chance a monster has to hit you. But dexterity also is your second line of defense; the higher your dex, the higher the chance you block the attack which passed your AC (and thus without shield would have hit you.)
For % to hit, AC, and dex needed for blocking, there is a roof; everything above these values is a waste. (These values can be found on Bolty's excellent page.)
So in short: Dexterity increases your chance to hit, decreases the chance for monsters to hit you, and increases blocking. Dexterity is the most important of these four for a warrior.
STRENGTH
Strength simply increases the damage inflicted by you. Strength is also needed to equip better armor or weapons.
MAGIC
Magic is needed to read books. Every point put in magic increases your mana with one. Of course mana is needed to cast spells. Reading glasses come in very handy! (More about reading glasses in part 12) tips in general.)
VITALITY
Every point put in vitality increases your hitpoints with 2. The more hp you've got, the longer you'll last. It's as simple as that.
HOW I DISTRIBUTE THE POINTS
As said before, dex is the most important of these four. Put most points in dex till it's maxed. My latest 2 warriors had it maxed at level 12 and 13. Before I reached those levels, I also put some points in strenght, just to be able to equip better items. I almost never put points in vitality or magic before I have dex maxed. (Remember I had it maxed around lev 13.) To read some books, I used reading glasses so I didn't have to put points in magic. (Later on you need and a good base magic and good reading glasses to get the spells to a decent level.) After maxing dex I also put some points in magic (still using the reading glasses I was able to read most books) and vitality, just to last longer.
So in short: Most points in dexterity, till it's maxed, and some points in strenth to equip better items. After your dex is maxed, put some points in magic and vitality as well (besides strength.)