Hi...
In addition to the above posts, allow me to add my $.02.
As mentioned, the Flight Review, (no longer called a BFR which was a Biennial, not Biannual), is required to be a minimum of 1 hour of ground and 1 hour of flight.
Typically what I personally do is this;
I'll sit down with the candidate and find out as much as possible about their flying habits as well as the frequency and so on.
Next, I explain that what I'd like to do is have them take a written test which I use as a guide to see where they may be deficient. I've actually found a pre-solo type test works best because a lot of the basic information hasn't been used in a while by some pilots. It's not a pass/fail test, just an indicator. I tell them the flight review will begin once I review the results.
I'll base the review upon the requirements of the Certificate held by the candidate. That's not saying if I have a Commercial Pilot I ask them to do Commercial maneuvers, but I will hold them to higher standards.
I'll start with Regulations and then we'll talk about all associated elements when planning a x/c flight. I prefer the x/c flight planning scenario when doing the ground because it will include Regs, weather, charts, etc. This is just an overview and can obviously be tailored to the specific candidate.
Hope this helps.
Regards