Lighting advice tends to assume a kit. Three-point lighting, a key and a fill and a rim, plus something on the background, which is four fixtures before you have started.
Most people have one or two lights and a window. Here is what that will actually do, which is considerably more than it sounds.
Start by turning things off
The first move in almost every room I have shot in is switching off the existing lights.
Domestic and office lighting is generally overhead, which puts shadows in eye sockets and under noses, and it is generally a different colour temperature from whatever you bring, which produces mixed lighting that is difficult to correct.
Starting from darkness and adding what you want is much easier than fighting what is there.
The exception is practical lights in shot — a lamp visible in frame — which are worth keeping because they make a room read as a room rather than as a set.
One light, done properly
A single source, placed correctly, with something to bounce it, looks better than three sources placed badly.
Put it to one side of the camera, at roughly forty five degrees horizontally and slightly above eye level, angled down a little. Get it as close to the subject as the frame allows and diffuse it — through a diffusion panel, through a shower curtain, bounced off a white wall or a piece of card.
Size relative to the subject is what determines how soft the light is. A small hard source produces sharp shadows. The same source bounced off a large white surface becomes a large soft source and the shadows soften.
This is why bouncing an inexpensive light off a white wall often looks better than pointing an expensive light directly at someone.
The fill does not need to be a light
With one source you get a bright side and a dark side. Whether that is a problem depends on the look you want, and a lot of the time the dark side is too dark.
A piece of white foam board, or a white sheet, or a white wall, positioned on the opposite side to catch spill and throw it back, will lift the shadow side without any additional fixture.
Moving it closer or further adjusts the ratio continuously, which is more control than a second light gives you at a fraction of the cost and setup time.
This is standard practice on properly resourced shoots too. Bounce boards are not a budget compromise, they are the normal tool.
What the second light is for
If you have a second fixture, the highest-value use is usually not fill. It is separation.
A light behind the subject, out of frame, aimed at the back of their head and shoulders, creates an edge that separates them from the background. Without it, dark hair against a dark wall merges and the image goes flat.
It does not need to be bright. A subtle edge is enough and an obvious one looks theatrical.
The alternative high-value use is putting something on the background, because an evenly lit flat wall behind someone is the most boring thing in video. A light grazing across the wall at an angle, or a splash of light in one corner, adds depth for very little effort.
Windows are the best light you own
A large window is an enormous soft source and it costs nothing.
The problems are that it changes through the day, that it is a different colour temperature from tungsten-balanced fixtures, and that direct sun through it is harsh.
All three are manageable. Shoot in a session short enough that the change does not matter, or on an overcast day when it is stable. Use daylight-balanced fixtures alongside it. And diffuse direct sun with a net curtain or a sheet of tracing paper taped over the glass.
Sitting someone beside a window with a bounce card on the other side is a complete two-source setup with one piece of card.
The mistakes I made for years
Lights too far away. Distance makes light harder and dimmer simultaneously, which is the opposite of what you usually want. Close and diffused beats far and bright.
Everything at eye level, which is flat and unflattering. A small amount of height creates the shadow under the nose and chin that reads as normal to us.
Symmetrical placement — one light either side, evenly matched. It looks like a photo booth. Asymmetry is what makes a face look three dimensional.
And too much light overall. Turning everything up produces a bright flat image. The interest is in the difference between the lit and unlit parts, and if everything is lit there is no difference.
What is genuinely worth spending on
If the budget extends past the fixtures themselves, in order.
Stands, because cheap stands fall over and a fixture falling on a person is a real event. This is the one place not to economise.
Diffusion — a proper frame with fabric, rather than improvising with whatever is in the room.
Something to control spill. Flags, or black card, or anything that stops light going where you do not want it. Subtractive lighting is at least as important as additive and it gets almost no attention.
More powerful fixtures come well down that list, because in a small room you are usually dimming what you have rather than wishing for more.