Basic /mjg/ friendly etiquette:
>Do not dama
>Do not tameron
>Reply "gg" when you leave
>Do not throw dora unless you are in tempai
>Do not throw an honor tile on the first turn
>Do not betaori (completely folding by dealing safe tiles)
>Do not break the rhythm of the game
>Do not suji-cut riichi (135p shape, throw out 5p to wait on 2p)
>Do not hell wait riichi
>Do not tanki riichi except for chiitoitsu
>Play according to the situation.

For me it's Double Aidayonken (1-7, 2-8, 3-9), Triple Aidayonken (1-8, 2-9) and Quadruple Aidayonken (1-9)