Spend some time polishing your mod. Those little details you paid attention to will shine in the mod and make people like it a lot more. It's tedious but it makes a difference between a mediocre mod and a great one.
Make backups often, because if you don't and if you mess up and couldn't undo somehow you will be scratching heads for hours maybe days. I know its an easy tip to remember but its something.
Coffee But seriously, a real tip is to listen to your audience; read the reviews, take suggestions, and always, ALWAYS be learning new things: methods, tools, etc. The more one does, the better they will be and their product will be.
