Amazon
If attacking from a distance is your thing, you'll love the Amazon's mastery of projectile weapons.
Single player TIPS:
Simply put, the Amazon is to ranged attacks what the Barbarian is to melee
attacks. At higher levels she is amazing with a bow and arrow, and if that bow
is magically enhanced and she has pumped-up attack and dexterity skills, she
is actually a force to be reckoned with.
The Amazon does have some skill with a spear, and should carry one of these
around in case she simply can't avoid melee combat. However, there's no use
having a spear unless some of her skill points are used to pump it up--for example,
with a Power Strike that can inflict lightning damage even at lower levels.
The javelin is a melee weapon that can also be thrown--and can also be pumped
up with some nice skills--but because skill points are so precious, players
are advised to pick no more than two weapon types to focus on.
It's also crucial to spend some of those skill points on Passive Skills such
as Inner Sight, Dodge, and Avoid, because the Amazon is liable to find herself
on the defensive a lot of the time. Players should also seriously consider developing
the Valkyrie skill (at level 30 or above), which summons a powerful warrior
to fight with the Amazon.
The Amazon's fighting strategy is best described as "hit and run."
Assuming she's using ranged attacks, she should concentrate on throwing or firing
and then backing away, keeping her distance in order to avoid melee attacks.
This is especially important when she is confronted with the inevitable group
of creatures. Picking off the creatures who come nearest one by one is an effective
way of dealing with groups--but she should avoid being surrounded at all costs
and should fight near a doorway, portal, or waypoint whenever possible. In fact,
doorways, corners, and even some outdoor locations can work to an Amazon's advantage:
instead of trying to fight an entire group, she should try to lure them away
singly or in smaller groups and kill them.
Once the Amazon has some gold, she should hire whatever help the town has to
offer, and make sure that the hireling has a skill that complements her own
in battle. These hirelings have a tendency towards aggressiveness and can die
very quickly in a fight, but will act as effective decoys when fighting the
game's boss characters.
Multi player TIPS:
In a multiplayer game, the Amazon should leave the melee combat to the Paladin
and the Barbarian and concentrate as much as possible on developing her ranged
attack skills. She should thus get a good bow--preferably a magically enhanced
one--and carry at least three full quivers of arrows with her. An Amazon who
wants to focus mainly on multiplayer should concentrate on building up her Bow
Skills, though if she finds herself engaged in combat away from the group, the
Passive Skills such as Dodge will come in handy.
In combat she is most effective hanging back and sniping at the enemy, since
her arrows will never hit another member of the party--so Bow Skills such as
Multiple Shot and Strafe are especially useful for thinning out a group of enemies.
If she hangs back far enough, the creatures fighting in a melee do not turn
and try to fight her if she shoots at them, making them easy kills. Another
useful Skill is Inner Sight, which weakens the enemy and thus makes it easier
for other party members to fight.
One thing to keep in mind is the effect latency can have on the Amazon. Since
she's primarily a ranged attacker, if you have a higher ping (say, above 300ms
or so), you'll want to train skills that don't depend quite so much on accuracy.
Skills like Multiple Shot and Strafe give you plenty of chances to hit your
target, whereas Guided Arrow goes the heat-seeking route--just fire and forget.
In a pinch, Freezing Arrow is a nice area-effect option, and as a bonus, it
locks your target so you can nail it with just about anything else. For melee
options, try Fend--it's easy to get swarmed by accident in high-lag situations,
and a "berserker lite" mode might just save your character's life.