Here are the materials:
1. A boring looking notebook
Doesn't matter if it's tattered or whatever. It will be covered sooner or later anyway.
You will need LOTS of papers. Some samples shown above are old magazines and art papers. You will need scissors for cutting things, glue and tape for pasting things, pencil/pens/colored pencils for doodling whatever design you want and plastic cover to cover your journal after you have finished designing it.
3. Some creativity. Do not stick with whatever I've written here. If you want beads on your journal, then go for it! If you want cloth-like covers then do it! Journals are personal things and that includes designing it.
Things to look out for:
Look for colors that represent you. I like these pink and purple ones. They look so happy and will look great as journal covers!
Backgrounds need not be plain. Go for crazy patterns!
I've been seeing lots of cool photographs nowadays. Why not use them as journal covers? I love this picture from a Hush Puppies ad, if I remember correctly.
Some Samples. I always place my nickname in my journals:
Even the letterings are cut out from magazines.
Journal with photograph.
Journal for little kids.
Keeping it simple.