Sharp ?
When you do a portrait you normally want a sharp face of your model. And most of us do portraits centered on the face of the model. That means the face will fill your viewfinder. But here comes the problem. How to get that sharp ?
You have to know that man will accept a face as sharp, when the eyes of a face are sharp. Even more detailed: The nearest eye to you MUST be in focus.
That´s the trick. Just set your focus point to the nearest eye and thats it. It will give you a wonderful portrait with one sharp eye and the rest is creamy bokeh ??? Don´t do that, only if you need an art approach. Remember: DoF is no absolute value but depends on the distance to your model. The closer you are the smaller the DoF. That means you can choose f5.6 to get both eyes pinsharp and the background is still creamy bokeh. But still focus on the nearest eye. Some cameras allow face detection in combination with eye detection. Often you can even choose which eye to take ( left, right or nearest ) Just consult you manual.