I think you are off to a good start, here is a little bit of what I see.
To get consistent skin tones take a meter reading on the cheek of your subject. To do this you can work in manual mode. Set your aperture and ISO, fill the frame with your subjects cheek, then adjust your shutter speed to get a zeroed meter reading, then I like to expose to the + side by +2/3 of a stop.
Vary the angles you shoot your subject from. A great way to make the subject look like a model is to lock focus on the eyes, then lower the camera and shoot with your camera at their neck level. Be sure not to change the plane of focus if you try this recompose method.
Watch your in camera crops. Your first image, your friends ear is too close to the edge of the frame.
i notice you have used flash in some of your pictures. If you follow my metering advice, you should get good exposure to let you eliminate using flash. Of course placing your subject in good light is a must.
Flash gives you pinpoint catch lights in the eyes. Large catch lights are preferred and can be achieved by placing your subject in good light.