One of the biggest challenges or obstacles when photographers move on to strobe or multiple strobe lighting situations is that often they complicate the matter. Often when people look at my group portraitures they think it must have been lit with a number of lights in a very complex way. The truth of the matter is that, it wasn't.
Lighting should not be viewed in a complex way. To me there are only three stages of setting up lighting for portraits; Background, subject, and hair/rim lighting and in that order. No matter what people say, you ALWAYS light the background of any portrait first. This is a general rule. Reason being the background is one of the key elements that allows you to shoot your preferred lighting ratio and preferred aperture. In some scenarios, the background doesn't need to be lit (ex. backlighting by a strong sun). If this is the case we first meter the background and then adjust the subject lighting/camera setting according to that measurement.
Most of the time when people light and they find the results not to their expectations, they start to add lights and gels and reflectors,etc... The problem is, I would say 90% of the time the problem is that they do not have the right lighting ratio and they are setting up their light by reference to technical data rather than using what is most reliable, their eyes.
When it comes to using a trusty viewfinder, or playback monitor, I can tell you that nothing is more reliable than your own eyes. The equipment only assists but your eyes should be the deciding factor. I think the problem with a lot of photographers today is that they seem to rely on equipment more than their own judgment. Lighting, like photography has not changed one bit since the beginning of photography. All the advance equipment we have today has only made it slightly easier but the science or theory behind making a good portrait has not changed one bit.
I have seen photographers that have simply placed a light because their experience or what they have learned in school told them to do so. The thing is each photograph is unique and carries it's own characteristics. Meaning that the lighting setup will be different from one photo to another, and just because in the last portrait photography session the 3 point lighting setup worked out doesn't mean it will in another.
I have seen so many people making the same mistake of metering the subject and lighting for the subject before lighting for the background. It might work for some people, but for me, I don't really get how can one light for a subject when not knowing the light measurement you are getting in your surrounding environment within your framing?
At the end if you still find lighting to be complicating and frustrating. Just take more photographs on location or in studio. Don't wait for a client to hire you, call out some friends and ask if they would like to have their portraits taken. The good thing about taking portraits for friends for free is that because they are not paying for your services, they won't mind if you experiment a little, make a few mistakes or take a long time getting your correct exposure (you don't want to do that in front of a client). Practise is the answer to great lighting in photography. To add on to what I have just mentioned about simplifying your lighting setup, I have drafted the following guidelines when planning your lighting for a portraiture.
1) Meter Ambient Lighting
Meter for the background and meter for the subject. Sometimes (outdoors), you may not even need to light the subject. Find out which direction your ambient lighting is coming from. Re-position if necessary
2) Light your background
3) Meter for Subject
When metering for subject most likely your light will not be dead center flat. Meaning that you should always meter left and right side of a subject.
4) Determine whether a rim light/hair light is necessary
5) If taking a wide group shot you may want to meter for hands, feets and dresses, just to make sure nothing is too underexposed (this is very important if you are using a very soft light with a strong falloff, the exposure can be drastic with very minimal distance).
At the end I will stress on knowing your lighting ratios. Knowing your cameras is not enough, because without lighting your 4k or 36MP stills or video camera is not different from any low end consumer end camera.