try it as a free player

Have you ever known someone who had all kinds of great stuff, and you didn't know how they got it? Well, it's a safe bet to guess they've done some begging in their time, while they probably won't admit it. While not the most honorable skill, sometimes people are just waiting to give someone some of their valuable junk.
Join a member's world. This really works the best if you are a member on a members' world. You can still try it as a free player, but the results are less likely to be successful
Go into a bank, any bank will do. The best ones are in Argougne, Edgeville, and sometimes the Taverly dungeon bank
Go into a spot where most people can see you, Wear the best clothes or armor that you have.
Empty most of your inventory into the bank so you have room if someone gives you a lot of items
Having done all that, say "does anyone have any members items i can have?" "I'm a new member" and "I'd never forget it."
Never say "plz" since many people find that incredibly annoying.
Beg for a little bit, and if no one responds, then stop.
If begging doesn't work (or if people respond badly, as they most often do) you should use some easy steps to make money:
Kill some goblins or men and take their money and bones. Sell the bones at the GE.
Kill cows and sell their bones and cowhides on the GE.
Collect spawned items and sell them on the GE.
Mine ore and sell it on the GE.
There are many other ways to make money that are just as easy as begging and won't make you look like begging scum to the rest of the Runescape community.
People occasionally pity you if you say "I'm a new member..."
When someone gives you something, be ecstatic about it even if you know it's not that great. "Tyvm!!" "Tysm!!" "You are so nice!:)".
People filter in and out of the bank.
Don't be obnoxious at all costs - it's bad enough