How to know a supervisor's working style before joining his group?

...never disturb to other colleagues. When I discussed with other colleagues...

Good for you!

My question is how would I know about these things before joining his group?

By talking with other members of the group, away from faculty, during your interview visit (or some other time before accepting the offer).

Conversations with students outside the professor's group would also have been useful. Also with the clerical staff. Even if unhappy group members themselves are hesitant to talk with strangers, for fear of reprisal, people know who the unhappy research groups are.

If the professor didn't actively encourage such conversations, that's already a red flag.

In addition to discussing with current members of the research group, it is often a good idea to discuss with students/researchers who left the group for another group in the same university (i.e., switched labs).

• Current members may be unwilling to give negative feedback regarding their advisor, especially if you do not know them well. If you're a prospective PhD student at a visit weekend, beware that current graduate students are sometimes asked to convince prospective PhD students to join.
• Members who left may have had a good reason to leave, and you probably want to understand it (is it because of the advisor/colleagues/funding/willingness to explore some of the research directions/etc).

I think that research departments should keep track of students/researchers flow between labs and make it available to new students/researchers, but unfortunately this is uncommonly done.

I would guess that the people that work the closest with professors are typically PhD students. They are also very much "exposed" to the professor's leadership style.

Often times the website of a research group lists the finished PhDs. Recently, I contacted former PhDs of a certain professor, because I consider joining his team. People were happy to share their experiences and I got a multi-faceted picture. Of course there may have been personal conflicts, so take their opinion also with a grain of salt.