Runescape is very different than real life (obviously). In runescape, you will find that whatever you say will not be taken seriously at first. If you ask someone to be your runescape friend, they might assume you’re a moocher and only talking because you’re after their runescape items.
But having a network of friends in runescape is part of the game. Somehow training is less boring, fighting runescape dragons is less scary and PKing is ten times as fun whenever you have runescape friends nearby keeping company in runescape. But making a runescape friend in runeScape is very different than making one in real life.
One of the best ways to make a good, lasting runescape friend in runescape is PKing. If you like to PK then find someone in runescape around your level. Ask them to team up (make sure they don’t backstab you!) and after you get your first kill together you’ll have a Runescape friend for life in runescape.
Another thing: if you’re selling an item to a runescape player and it’s a fair price (it should be), then don’t hesitate to chat about stuff outside of the trade about runescape. You might find that you’ll make a lasting runescape friend this way not to mention a reliable buyer in the long run in runescape.
Make sure, however, that you don’t expect anything from them. Sure, Runescape friends do favors for each other, but make sure you don’t require them to. The most common mistake that screws up Runescape friendships is one person demanding something from the other just because he’s a friend in Runescape. This is a serious no-no: don’t act desperate and don’t be a leech, and you’ll have your friends list filled up in no time in Runescape.