they already posted this for you in your link, but anyway...
Only trade in game.
Do not take cash (people can put in a fraud charge on PayPal, get there money back and you're screwed)
Do not take forum gold. Someone will gladly ruin their D2jsp reputation to make the real money they can get from flipping that themselves.
Do not drop it on the ground.
Do not trade it by dragging it to the trade window, only right click to add it to the window (you might miss the trade window and drop it on the ground).
Say you sell it for 100 billion (pinkie to lip) gold, have them input the number as 100111222333 or 100111000111 so you can easily count each group of digits. Much easier to see this is 100 billion than 100000000000.
Have the buyer select "accept" first, double and triple check the price is as agreed and then click accept.
Enjoy your small fortune in D3 or cash it out for Radiant Star Emeralds on the RMAH for quick cash.