test the water(s)

to try to discover what people think about an idea before you do anything about it, or to try to discover what a situation is really like before you become very involved in it.

Example:
Perhaps you should go to a couple of meetings to test the waters before you decide whether to join the club.
或許你該參加幾場他們的會議，再決定是否加入這個俱樂部。