It does depend on how much you already know, what you are looking for and how close you are to the family members.
Start with what you know and let them fill in the rest. People will add to or correct, the blank form can be daunting.
I've had mixed results with relatives, some will give you a lot of info, others just won't.
You can follow up with emails and phone calls, but unless you are in the same room, you can't be sure of results.
I record the conversation, if I can. Using an app on my phone is less intrusive, people forget it's on.
I had a phone call once with a cousin, I tried to keep her on track, but things went off the rails pretty quickly.
Memory is a fluid thing, it meanders and wanders and connects in strange ways. Older relatives can get tired, or emotional. You have to legislate for that.
If you search for family history questionnaire genealogy, you'll find some great lists of questions.
Looking through them will give you an idea of how broad you can go.
There are some useful forms online, I searched for: family history form genealogy