Keeping a sketch book is one of the most valuable habits to get into for your art practice. I have all the sketch books (or visual diaries) since I was in 3rd year at art school. That’s 20 years worth of ideas and observations! It is a valuable resource when starting a new artwork.
Scribble Book
My sketchbook is more like a scribble book than a book of finished drawings. It is a reference point, not a finished product. If you think of it as having a scribble rather than drawing, that can make you feel free to draw whatever comes into your head. Its important not to censor yourself at this early stage, feel free to doodle, let your mind wander. Do not judge yourself. This is for yourself, not for anyone else. Many of the things I draw are more to help me remember what I had in my imagination at the time.
Holidays and Travelling
When your on holidays or out of your usual surroundings it frees up your mind to think about things differently. When you are out of your normal routine it gives you perspective on your life and you look at new surroundings with fresh eyes. This is a great state of mind for making art and your sketch book is perfect, small and portable. I have visual diaries from years ago when I taught English in Japan, when I backpacked through Europe and when I went to Melbourne for an exhibition I was in. Not to mention all the other small local trips and holidays.
Some of my drawing is about recording interesting things I see. Architecture or natural landmarks, the way a bay curves around, the shape of an interesting tree. Other times its ideas from my imagination that have surfaced because I am in a new place and not thinking about normal day-to-day concerns.
Not just for Drawing
See an interesting image, if possible (and legal) glue it in. An invitation to an exhibition, a photo, an image from a magazine, a postcard, drawing scribbled on the back of an envelope, interesting leaf…..glue it in.
Other Inspiration
My life and the lives of those around me are most of my inspiration and all sorts of things can feed into ideas for making art. A lot of my work is narrative and I tend to see stories as pictures so all sorts of things feed into my art practice. Something someone said in a conversation, song lyrics, reading a novel. Whenever one of these things gives me an idea I scribble it down in my book straight away before that image fades from my head.
What type of book?
I’m a sucker for a beautiful blank book, but sometimes they are too nice. I have had a book that was too special for scribbling (that one I put more finished drawings in). At the moment I am using hard bound black covered A4 books in the past I have used the spiral bound version too. Don’t buy one that is cheaply made or has low quality paper, I like it to be a pleasure to draw in. It has to be strong and robust, a hard cover is good too. Choose whatever size suits you. I use A4 mostly but sometimes for travelling I have A5.
When I need to make a painting for a themed exhibition or some other kind of finished artwork, I just flick through my most recent sketch book, the pages are laden with ideas. If I don’t find anything I go to an older book. With all those scribbles I’m bound to find something.
Check out my website to see the art that came from the sketch book scribblings. http://www.shanajames.com/
Art - Ideas and Inspiration 
Yes, I often combine different ideas too, things that I may have drawn months (or even years) apart may combine to form something new. Finding those things that go together is really enjoyable, sometimes I feel like they choose themselves. Thanks for your comments I love to hear what other people think.
The value of a sketchbook cannot be mentioned often enough. As most visual artists I have my head full of ideas and a lot of them would just disappear if I would not keep them in my sketchbook. Sometimes even a few keywords are enough to remember what the idea was about later. I often experience that an idea I had is not really useful for an artwork, but it can lead me to something new. Or I start to combine different sketches from my book to create a new artwork.
Using sketchbooks can open a whole new world to me and each time I go through them it’s a different journey with different artworks at the end.