Up your shutter speed in order to ‘freeze’ your subject, or to avoid camera shake.
Use a tripod to steady the camera when you are having to use a slow shutter speed.
Use a higher F-stop to narrow down your aperture. A higher your F-stop (aperture setting) means you will have a larger area of focus to work with.
A good way of getting your head around this is placing an object (let’s say your finger) right in front of your nose and focusing on it; your eyes will adjust accordingly and only place focus on that finger, the rest of your surroundings will be blurry.
If you then point that finger as far away from your eyes as possible, you’ll notice that more of your surroundings will be in focus behind your finger.
A wide aperture (small number) is like having your finger close to your eye, a narrow aperture (bigger number) is like focusing on your finger when it’s furthest from you.
A wide aperture will give a shallow depth of field, whereas a narrow aperture will give a deep depth of field. An ideal, all-rounder aperture to use is f9, and this f-stop is sometimes referred to as the focus 'sweet spot'.