Write about your artistic experiences, ideas, adventures, and frustrations. It will help you connect with your work on a deeper, intellectual level which equals more ideas.
2. Record your process
Document the stages of your art or design (photos or screen grabs), paste the images in your book, and annotate them (what worked, what didn't, what were the digital settings, and what would you like to try next?).
3. Document your inspiration
Print or clip inspiring art or design and write a sentence or two about why you liked them and how you can use that in your own work.
4. Experiment with new mediums
Explore new mediums in your book. Graphic design is largely digital now, but traditional mediums are often scanned and incorporated into the final design and some people still work in traditional mediums, so traditional is a handy item in your skill-set.
Draw in your workbook, even if you are not a drawing major (try a combination of sketches from objects in life, photo copies, and imaginative sketches). Also, drawing can speed up some of your graphic design process: for example, it is faster to draw logo ideas and then pick the best to digitize rather than doing all the exploration on the computer (one of those funny facts of life).
6. Draw your inspirations
If you are a graphic designer, sketch found graphic design (drawing someone else's poster will help you really see it in a much deeper way than snapping a photo).
Legally, this one is very important. Remember to cite the original sources of work that is not your own (photos, copies you drew of someone else's drawing, etc) and ask permission before posting online (citation is not enough for posting or republishing--more on that in a later post).
Remember, the biggest tip is to stick with what works for YOU, no matter what others say. If you are a graphic designer and you love to paint watercolors too, don't let people deter you from a process that helps you grow. I love to write in my workbook and I document anything from design ideas to passages about artistic challenges. I've had people tell me that I shouldn't write in my book because I am a visual artist and my book should be visual, but I found that my creativity dropped when I didn't write in my book. Explore everything you can think of, give advice a try, but stick with tips and ideas that help you. If a tip doesn't help you grow, then it's not advice.
Now enough reading. Get out there and dive into your books!