You may think a guide is not needed for looting, maybe you are right, but you will find these tips very useful.
1) Pick some lame armour, don't go naked, people love killing looters, but they wont waste food on a guy with shitty armour.
2) Turn auto retaliate off.
3) Loot at world 1.
4) Loot at Edgeville, the bank is very close. (plus you respawn next to the bank).
5) Have 4 or 5 lobsters in your inventory. If you take more than that you will end up eating them or dropping them to pick the loots.
6) Rangers are your best friends, they drop arrows, bows, coifs, and food.
7) Walk into fighting rangers, you will make it hard for them to see their LP so they will move and you can pick their arrows.
Pick all the stackable items like arrows, runes, coins, etc.
9) Pick all the items that can stack in your bank (they wont take a new bank slot).
10) Don't just pick the adamant arrows and "expensive" stuff, the money when looting doesn't come from rune items forgotten by the killer, but from "not-so-expensive" stuff that people don't take.
11) As soon as your inventory is full bank your stuff.
12) The wilderness is full of looters, be creative when picking items.
13) Here's a list of the items you should take when looting:
Adamant arrows
Mithril arrows
Steel arrows
Lobsters
Swordfish
Monk Robes (they are like 1k a piece)
Maple shortbows (200gp each and they are everywhere)
Coifs (50gp each, but sell them for 1k each at the GE, they sell)
Rune, Adamant, and mithril items.
Amulets of power and strength.
Leather boots! (100gp each, they are everywhere and sell for 500gp+)
Wizard hats (black ones are 200gp each, blue ones are 500gp each)