How do you exclude certain areas from being sharpened when sharpening?

Often an individual R, G or B or other channel may make a good start point for a mask – as the most natural selection is not based on a "synthetic" selection.

Another approach I like is to use High Pass sharpening with a twist.

In its regular form you add a copy merged layer to the top of the stack and apply the High Pass Filter, then set that layer's blend mode to Overlay. You can also use Hard light and Vivid light but the effect becomes harsher.

Here again it makes sense to make the High Pass layer a Smart Object.

The twist I use is that if the image has some noise (like from using a high ISO setting in poor light) you can apply noise cancellation to the High Pass layer so just the high contrast areas are sharpened without the noise being exaggerated.

If it is a multi layered document, make a copy merged layer at the top of the stack (Shift Ctrl Alt E)

Sharpen that layer.

Add a layer mask and paint out the areas that have become over-sharpened.  Note if you use a low opacity brush in the layer mask you can build the removal of the over-sharpened areas.

Or bettwe still, make the layer a Smart Object. Apply your sharpening, and mask out with the SO mask.  The advantage with this approach is that you can adjust the degree of sharpening as many times as you need.

Or use Sharpen > Unsharp Mask and adjust the Threshold slider.  This looks at the difference between adjacent pixels.

Easy Image Sharpening with Unsharp Mask in Photoshop (photoshopessentials.com)

Sharpen on a duplicate layer and put a mask on that duplicate layer.

There are more advanced approaches involving smart objects and smart filters, which will allow you to go back and re-edit the sharpening later - but start with the basics.