In the layout stage, head turns tend to be surprisingly simple. The minimum expectation for a layout artist is drawing the start and endpoint of the turn. Its useful to go "off tap" (Tap wari) when doing head turns. You can do this to match up different parts of the head exactly and ensure you're not going completely off model. This is really useful with the eyes, since they change drastically between front and side views but you need to keep the size and proportion consistent.

In some cases, it's helpful to use either a third key or an inbetween guide at the halfway point.
A lot more goes into turning your head than just swiveling it on a flat plane. Most experienced animators I've spoken with recommend that you draw the head tilted down slightly with the eyes closed if you include the middle drawing. It makes for a much more natural head turn.
The eyes also tend to "lead" a head turn, which means they look in the direction the head will turn before the motion starts.
I'll do a more detailed breakdown of what actually goes into a finished head turn in the douga section. I recommend you look at that section to understand how your layout work is translated into a finished set of drawings. It will be super helpful in your decision-making process for head turns.