Buying and selling

Can't make something yet? Buy it at the Grand Exchange. Get there from the exit portal in your garden (its Grand Exchange row) and press H or the House button to go home.

Offers

Talk to a Grand Exchange Clerk to place a buy or sell offer for almost anything (not uniques). Your coins are taken when you place it; the offer fills over real time, even while you're offline, straight into your bank. You can abort what's left.

Merchants

Specialists sell their trade at once, at prices that move with their stock: Grand Exchange Clerk (anything you've got), Hofuthand (weapons and armour), Farid Morrisane (ores and bars), Relobo Blinyo (logs and planks), Bob Barter (herbs and potions), Murky Matt (runes and essence).

The black market

A shady stranger sells a few rares at a steep price, a new selection every few hours.