Choosing a menu item with 〜ておく

Grammar Explanation: Doing in advance with 〜ておく

Looking over the menu of tea choices, Rize wonders which will be appropriate for her.

リゼ:: 「適当(てきとう)に選(えら)んどくか」; “Shall I just pick something at random in advance?”; Literal: “Shall I choose something randomly and leave it done?”

Note that 選(えら)んで + おく is contracted here into 選(えら)んどく.