My first answer is ‘why are you asking me?’ but the other day I learned something that had been bothering me for a long time.
1 If you are hand holding your camera, no matter what focal length your lens is, your shutter speed must be greater.
If your focal length is 150mm you must shoot above 1/150 shutter speed.
If your focal length is 50 mm you must shoot above 1/50 shutter speed
and so on.
This has caused me a great deal of frustration until I learned that just yesterday. In fact, I knew it about a telephoto lens, but I didn’t know it about a macro or kit lens.
2. Use a tripod and remote shutter release whenever possible, even in the light of day.
3. If that is not practical, which of course it isn’t, make sure you are not too close to your subject.
4. If you are using auto focus make sure you are focusing on the right thing. If that is difficult, use manual focus as I had to yesterday when trying to photograph a spider web.
5. Hold the camera as steady as you can.
6. Make sure your aperture is appropriate for the subject. Remember something like f1.2 lets in more light but has a very narrow depth of field. Something like f16 has a slower shutter speed and lets in less light.
7. If you are shooting in the golden hours, definitely use a tripod.
8. Things move. I was trying to photograph a lavender field the other day, but it was windy. It was also too cloudy for me to up my shutter speed. So the lavender was out of focus.
9. You need a really high shutter speed when shooting moving objects.
10 Sometimes you may want a blur for artistic effect. So you use a tripod and shoot with a low shutter speed. The static objects will remain in focus but the moving ones will blur. Sometimes that is a very nice effect, particularly with water.
11. Make your ISO greater if you need more light and better shutter speed. That can make photos grainy though.
12. In macro photography, a really large aperture like f1.8 will not get all the subject in focus but it may be the effect you want. If you want the whole of the subject in focus (depending on how big it is) use a smaller aperture like f11.
13. There is a ‘sweet spot’ on every lens. That means the best focus on what aperture.
14. Lenses do matter. My kit lens is really pretty hopeless, but my macro and telephoto lenses are okay. But you really need a professional lens (the L series) to get the best focus.