Adjust the switch on your lens for M (manual focus) or to AF (auto focus).
Learn to use your camera in manual focus mode. Turn focus ring until your subject looks sharp. Focus on your subject eyes when shooting a portrait. The eyes must be sharp for a successful portrait. And think about depth-of-field. A wide aperture will give you a shallow area of focus and a small aperture (lens opening) will give with a broad area of focus.
Once you are comfortable with manual focus, learn to focus your camera in auto focus mode. Look in your camera menu for options on auto focus, like tracking options for a moving subject. Learn to set your cursor for the area you wish to focus on. Press shutter half way to activate your light meter and your focus. Look for areas of sharp contrast to focus on to quickly lock your focus in.
When you set your exposure for a subject in the shade or on a cloudy day, you will have plenty of exposure latitude. If you want your subject to be bright, snappy and high key, this latitude will allow you to over expose by a stop, which will make your photo pop and key your colors bright.
When you set your exposure for a subject that is directly lit by the sun, your exposure latitude will be narrow. If you over expose your highlights they can blow out. If you under expose the dark areas of your subject you might clip your blacks. So be careful with your exposure reading.
When you photograph inside you will still need to look for good lighting for your subject and you also need to be careful about your white balance. Avoid situations where there multiple light sources of different white balance. This will make color correction difficult in post.
Always use your light meter and histogram to capture the proper exposure. And when you review your shot on the screen, zoom in to check the focus. There are usually a + – buttons on the top right on the back of your camera for this purpose.