What is the quickest way to chat with someone?

[I cant Speak chinese]

I keep have to going into friends list and then select send message. Is there a more quicker way?

Without having to type/whisper 33404-33233e2^^$%64

[Twoflower]

You can aim at them in game, hold the spot key (default Q) and select Send Message from a wheel.

Alternatively, if they've already sent you a message, you can type /r to reply

[VII Imperial Fists]

press alt in right click them on the chat screen

[Nokta]

If someone already sent you a message, you can reply by typing just

/r

[MadMarco]

If you have received a message by this person, just type /r in chat and then your text. Your friend can do the same after you wrote him.