Here is my list:
1. Don't beat your self up about not being creative every day. Sometimes, in order to be our most creative, we need to rest from trying. Very often, the most creative ideas come to a rested and relaxed mind.
2. Draw. anything. Just sketch what you see, and sketch what you don't see. Doodle, scribble, scratch, push and pull. And do it often.
3. Take a walk outside. And if you have time, take your sketchbook with you.
4. Back away from your project for a few hours. I know that sounds counterintuitive to the process, but it really should be the first rule. Fresh eyes make for fresh perspective.
5. Learn a new technique. Or if you're tapped out on technique in your field, try learning a new art. (it will actually help you in your current art.)
6. Buy a new tool.
7. Get some new supplies.
8. Play with kids for a little while. Let them show you how they create.
9. Get out some play dough or silly putty. Not only does it relieve stress (which can seriously limit creativity, but it might lead to new idea!)
10. Clip out photos in a magazine that you like.
11. Go to a flea market. Take your sketch book.
12. Take a road trip. Take your sketch book - and a camera!
13. Take photos often. Of boring things. It'll make you see things in a new way.
14. Do some blind contour drawings. It'll get you in tune with line and shape.
15. Go to a fabric store and clip swatches of textiles that you like. Take them home and look at them.
16. Make something random without thinking or caring about what it will look like. Just start.
17. Challenge yourself. For instance, join in on something like the Ring a Day project.
18. Join a group of people who are doing a similar thing as you. You all will spark creativity in each other.
19. Organize your working space. You might find things you forgot you had, to work with. And it's kind of like getting out a fresh new sheet of paper. You gotta love that!
20. Exercise your body. It'll really help your mind.
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