Icon Best Practices and Guidelines

Use the following checklist for icon best practices and guidelines to help you avoid the most common mistakes :

1. Don't reinvent the wheel. Familiar icons work best (e.g. home, close, print, play, search). 
2. Use icons to save space and improve recognition in toolbars, functions, and navigation.
3. Icons should be fast to recognize. Use icons that people have seen and used before.
4. Don't change file type icons for file downloads. For example, use a “W” in a blue box for Word. 
5. Icons should always communicate meaning. Don’t overuse them or use them for decoration. 
6. Use the 5 second rule: If it takes more than 5 seconds to think of an icon, it will probably be ineffective.
7. Icons must visually describe the function and purpose. Make them simple, familiar and meaningful. 
8. Always have at least 1 cm x 1 cm minimum around the icon for legibility and easy tapping on mobiles.
9. When large enough, icons make good targets on mobiles where space is limited. 
10. Use a single icon set and ensure that all your icons are consistent and cohesive. 
11. Always use labels for icons and show them to the right or below the icon. .A good test for an effective icon is when users can tell what it represents without a label. 
12. Don’t use icons with conflicting meaning. Icons that could represent multiple things should be avoided. 
13. Be careful with "heart" and "star" icons. They can mean different things and often confuse users.
14. Keep icon designs simple and schematic. Minimize complex shapes and graphic detail. 
15. Make icons distinct shapes and colors. This helps users recognize and recall them.
16. Avoid using similar icons for different purposes or different icons for the same purpose. 
17. When in doubt, remember the best icon is a text label.

(source: Intechnic)