1. Have a folder on your computer or phone or even in an actual folder of images you like. Paintings and photographs and drawings, things that you like for whatever reason. You can draw on these images based on themes or colour schemes or shape, what ever you need. This is similar to when art teachers hang up work around the room, except it's personalised.
2. Music. Over time, you'll find music that you listen to more often when you're creating. Listen to it, and work like that. I've found that movie soundtracks and other plain instrumentals work very well for me.
3. Experiment with colour. Just take your pencil crayons and draw. Look at what colours match and what colours don't, and go from there.
4. Wait. Just sit for a few moments, close your eyes and envision what you might want to do.
I know that these might not work for everyone and might sound kind of ridiculous. I've gone through long periods where I haven't created anything, and that was a pretty bad feeling. I've been slowly working and searching for ways to improve my creativity and productivity. The best part? I'm still a student! I have all the time in the world to improve, and I'm starting now.