Less is more: Do not overdo with the editing. I know editing is fun and while editing the maximum layer you will put will look beautiful. But after finishing it will look unnatural.
Overcropping: though I said before always make an option to cropping a photo but never over crop it. It may ruin your picture quality.
Do not rush: Take your time when you sit to edit a photo. Rushing will not do any good for your photo.
Do not try using multiple programs: if you are not a pro and try all the program came up to you it will not do any good. Stick to one and learn it properly and then see what magic you can create with that.
Do not overdo texture: Texture can be fun. And if you are a fan of texture it is ok to use it, just go easy with textures. Otherwise, it will be unrealistic.
Know the curve: when it comes to shadow and lighting you have to know the curve. Every person’s creativity and taste are different. The curve differs from one another. So discover your one and master it.