Learning about icons and icon styles
Icons need to be very descriptive; they should be a simple representation of their original function. You don’t need to reinvent anything, just do your research, and pick the metaphor you need. Be creative but aim for the easiest recognizable form.
After all, you want the user to recognize what is pictured by the icon. Safety? A lock, a key, or a shield are all safe bets. Speed? A speedometer or a flash. Ideas? A lightbulb or a brain. These are all common symbols you may use in your icons to make them instantly familiar to users.
Having a clean and recognizable form also helps with scaling. We usually design icons to be pixel-perfect in a small size with given measurements in mind. The times of using only 16x16 pixel icons are long gone; now, end users are used to seeing icons anywhere from 24x24 up to 180x180 pixels.
When you finalize an icon, it still has to cater to be used in small sizes as well. Keep the shapes of the icon clean...