Pking as a Swordsman
When you are Pking as the first and most important rule is never mess with mages because your armor increases the strength of their attacks. The second rule is always having food recommended that you have swordfish or lobsters.
You best bet is to attack archers it's hard for their arrows to penetrate your armor and your weapon (recommended scimitar or battle axe) will easily hurt them due to their lack of armor. If you do ever have to fight a mage and u cannot run I suggest you take your armor off. Oh and always have a power amulet helps with a lot of your stats.
Pking as an Archer
Archery is harder than a swordsman because u have to pick up arrows before you run out which allows the opponent to attack while you are getting them. When Pking as an archer you should stick to fighting mages because you should have leather helps stop the attacks of mages. If u r ever in a fight with a swordsman u shouldn't sweat it because both of u will do a decent amount of damage but he/her will still do better.
Pking as a Mage
Pking as a mage would probably be the easiest because a good mage can teleport, bind there enemy, and curse them and if you have a high prayer level u can protect your items. When u r Pking as a mage always try to fight swordsmen because like I said before, their armor increases your attack.
When Pking you should always have some type of magical staff and the runes that allow you to teleport. If you find yourself fighting an archer just run away or teleport.