At its core, the Grand Exchange for RuneScape Gold is a very simple system, and you can buy or sell items and Buy RuneScape Gold using the following steps:
Bring items that can be purchased with Cheap RuneScape Gold you wish to sell or RuneScape Money to buy items.
Speak to one of the Grand Exchange clerks to either put items or RS Gold up for sale or to make a bid to buy items with Cheap RuneScape Gold.
The clerks will take your items or money and look for a matching bid/sale to match you up with.
You may have to wait for your bid for RuneScape Money to be accepted or for the clerks to find a buyer - then again, it could happen in moments!
You will receive a message about Cheap RuneScape Gold when the trade has been completed, and you can go to the Grand Exchange or any bank to pick up your purchases or money.
You cannot buy or sell untradeable items purchased with RuneScape Money using the Grand Exchange and there is a small handful of tradable items that cannot be bought or sold on the Grand Exchange for RS Gold.
All of the trades that the Grand Exchange manages are between players who want to Buy RuneScape Gold. No items are ever made or destroyed by this system - they are simply transferred from player to player. Your offer to buy or sell will, therefore, only be completed if the Grand Exchange clerks can find another player who want RuneScape Powerleveling to match your trade with. You will not know who you have bought items or RuneScape Money from or sold them to, but you will always get a good deal regardless.