I will try to add a few more information valuable enough to solve your problem:
Most valuable tip: Always make sure to have all your hotkeys set adequately! Potions, rings and speed sets, defensive imbuements and protection sets can be used according to what you can carry/can afford. Try to figure out the best way to dispose all of it on an efficient way! It depends mainly on how you play Tibia, changing from player to player.
Now, regarding other important hints to be said (some of them may have repeated content. I will try to elaborate the best topics to be looked upon):
1) Have friends/be friendly when interacting with the server community: The more friends you make, the better is for your reputation, and also you may eventually find a good friend that probably will come after your PK attackers during your hunt (a friend that trust on you will certainly provide.
2) Carry more potions that you usually need on huntings/quest. Do not wait for your supplies to almost end before ending your hunting session. PKs can be tracking you and may find more lucrative (and easy) to attack you after a hunt. By the way, having a energy ring, time ring and stealth ring can mean a lot on emergencies, even if you don't use them often,
3) Try to carry almost every usable offensive and support rune in order to save yourself from danger: Elemental bombs or walls may grant you a safe spot in case of places crowded with monsters. Putting a few elemental fields may as well help you against regular summons or enemies going up and down stairs/holes. Soulfires will make the PK stay in the game if you manage to push back against him. GFB can be a great way to wipe out weak mobs blocking you path (specially if you are a weak Knight), disintegrate runes can be precious against several garbage items crowded on a SQM (sometimes it will mean that you won't be able to push an enemy before getting rid fro, the garbage on the SQM). Destroy fields can clean elemental fields, and Magic Walls/Wild Growth can block the path that your enemy is following you. Going offensive can be a surprise for PKs, so try to carry some SDs or/and paralyzes with you in order to deal some blows before running away.
4) Always look for holes/stairs/passages in order to make last stands, gain time before reinforcement to strike back the PK or simply in order to make the PK give up on you
5) Do not wander around mindlessly. Always be prepared and well equipped, but most important, be aware about exits and potential dangers around. PKs can recognize a novice, but still, if you are aware about the environment around you, you can make the best to run away and find cover on a PZ or out run the PK on a crowded place. Sometimes you can unlock rooms with ongoing quests opened or after completing one. They can mean the salvation for you, but you need to know the terrain in order to prepare your escape route.
6) Do you want a safe refuge? Carry keys (Hellgate Key, Carlin Bone Key, etc) always! This one can make a Free Account save himself even from Premium attackers! If you know that you may take refuge on locked rooms, try to make use of them!
7) If you are Premium account, do not underestimate basic spells as Levitate, Haste and Magic Rope! Have them on hotkeys equipped!!! They are cheap and can save your life easily. Against a Free Account attacker, a Levitate on the right spot can simply deny any other aggression if the aggressor forgot to carry parcels!
8) Check your guild politics stances on the server. Be aware that being on a guild means that you will respond to any alliance or aggression made by your members, leader and vice-leaders. Sometimes even personal problems from other players may cause disputes that will mean random PKs on any guild member. Make sure to be on a serious guild that is very serious and transparent on interactions, informing members constantly and demanding a coherent conduct from each member.
9) Watch out about shady requests or "secret quests" that involves accepting parties invitation or throwing fields on the ground. They usually lead to a accidental skull or to a dangerous place where you can't runaway from PK.
10) Carry around most of basic tools: Machete (cut grass, excellent on Venore swamps), scythe (sometimes you can save your self and make your sides protected on a wheat field cutted, making physical close range enemies attack you only one by one if they can't cut the wheat), crowbar (it can open doors on Tibia, but not everyone knows about that detail often overlooked). You never know when they will be fit for use. Flowers pots can be strategy too if you want to block passages as well! Pay attention to your cap limit!