When you see something hit the ground, click! Chances are that you are competing with other people, and the person that dropped stuff dropped more than one thing.
There are two types of things you can kill to get stuff for free: Computers or other players. You have to be strong, with a good range of fighting skills, heavily armored, and fast! You don't have to buy runescape accounts and pay runescape gold for everything! Of course, as you become stronger and can fight harder creatures, they'll drop more valuable items. If you don't feel like fighting or working for free stuff, than just find drop parties. Once you have a target, watch the ground beneath them at all times. You have to be quick if you want to be able to get something. The best begging spot is Lumbridge, because that's where newbies begin and where dead people start all over again. Though runescape account selling is the lowest thing to do, begging requires patience, and the appearance of being poor. Even if it's just some bones or feathers. If you are a low level, I recommend killing goblins. The good thing about fighting other players is that they'll drop really good and valuable stuff, since you only keep three items when you die.
There are plenty of ways to get free items and runescape accounts for sale on runescape.