Make sure you have decent AC and HP's, especially at L20+

L1 to L13 - Have a friend pick up a bunch of Rod's of Lighting from New Genesia shop. Expensive, but a fast way to level.
L14 to L20 - Invest in Oak Staff's from Riverton Shop and use them like water. Again, expensive, but fast.
(Note: If you are Good, keep using Rods of Lightning)
L21+ - Rods & Staffs become too Expensive to use 'cept as backups weapons, and Spellcasters Spells are getting close to having that level of damage output.

CLERICS
Preferably...Find Grouped Mobs and use area spells.
Target Grouped Mobs around 1/2 of Experience Cap.
Target Solo Mobs around 3/4+ of Experience Cap.
Spell Order: Faerie Fire, Poison, then Blind.
Dispel Evil does 100dam for 15mana. Very useful at low Levels!
Dispel Evil will target YOU if you cast it when you are Evil. Dispel Evil will cast Armor on Good Targets (including yourself)
Harm does 4x Your Level in Damage (it Heals Undead).
Hammer of Faith only works on Mobs of Opp Align from Caster.
Heal heals 3x Your Level when cast on yourself.
Heal heals 6x Your Level when cast on someone else. (So ALWAYS cross heal if there are multiple Clerics)
Protection from Good/Evil cuts damage from Opp Align mobs by 1/2. (But you cannot be Neutral and cast these spells)
Rainstorm & Lightningstorm increases spell damage for Call Lightning.
Fireshield will not stop PK'ers, but will annoy them... Phantasmal Images will slow down a PK'er long enough for you to flee.

MAGES
(Note - Solo'ing a Mage under L20 can be very difficult)
Preferably...Find Grouped Mobs and use area spells. Before Manashield, pick on mobs under 1/2 your Experience Cap.
After Manashield, try 3/4+ your Experience Cap.
Spell Order: Faerie Fire, Plague, Curse, then Colour Spray.
Colour Spray causes damage, and blinds mobs easier than a Blind Spell.
Use Charmed Mobs for tanks, or Create Elementals if you have stones.
Your Spells do more damage if you are currently at Max-Mana.
Being Underwater increases the spell damage for Shock wave.
Rainstorm & Lightningstorm increase spell damage for all Lightning Spells.
A Fireshield/Manashield Combo will keep most PKers away from you.
(But only while they're up, Teleport away if someone Dispells you).
Phantasmal Images will slow down a PKer long enough for you to flee.
Use Farsight and Shield Room in Aggresive zones.
Shield Room will help protect you from Hurricanes, but not Wasps.
Keep yourself Invisible at all times, especially in Aggresive zones.
Make sure to keep a large supply of healing items at all times.
Don't forget that you can Teleport away in an emergency.
Keep your Wimpy very high.

THIEVES
BS Solo Mobs that are at least 3/4+ of you Experience Cap.
Target Grouped Mobs that under 1/2 your Experience Cap.
If using the...BS, flee, BS, flee method, Set Wimpy to Max.
Avoid Mob forms unless using Staff's.
Trip Spellcasters if you fight them, it disrupts their spells.
Don't use Offhand while you are BS'ing, use a HR/DR shield. (it adds to the BS damage that way, offhand won't)
Throw can be useful, but you can not use a holdable while doin it. (get a L31 Mage of your alignment to enchant your throwing items)
Always sneak after killing a mob (better yet, set up a trigger)
Make sure to have healing items for emergencies. Scan often, especially in aggresive zones.

WARRIORS
Target Solo Mobs between 1/2 and 3/4 of your Experience Cap.
Target Grouped Mobs under 1/2 of your Experience Cap.
Avoid Mob forms unless using Staff's or Charge.
Bash Spell casters if you fight them, it disrupts their spells.
Charge Grouped mobs you fight. Kick solo non-spellcasters.
Make sure to have healing items for emergencies.

GENERAL NOTES
Set up a trigger on your Mud-client to auto-wield you weapon if disarmed.
Always try to rest up to Near-Max HP's and Mana before starting a fight.
Make sure all your Protection spells wil l last as long as the fight.
Keep Detect Invis, and Sense Life spells goin at all times.
NEVER sleep in NPK... If you get CPK'd, don't complain...you walked in, nough said.
NEW Spells for you current level Cost 50mana unless the spell costs more.
When in PK areas, keep Sanc or Fireshield up at all times!