If I had to give only ONE tip, it would be to practice observing - to take photos without fear or self-judgment, just for the sake of observing, experimenting and learning. This tip is a valuable one for beginners and professional photographers. It is ultimately what allows photographs to convey feeling.
But today, I'm not giving you just one tip. I'm giving you 10. Here are some of my "photography mantras", which I practice daily.