Since I am a firm believer in not reinventing the wheel (not to mention it would be a very long post), I am going to direct you HERE for wonderfully clear and easy instructions for the basic bookmark shape. The instructions by Beate at the link I've provided are clear, concise and VERY easy to follow.
I stamped Lili onto X-Press It brand card and colored her with my Copic markers. I actually colored the entire image (all the way to her little feet) and did a really nice job of it (if I say so myself), so I ended up making two photo copies of my colored image onto white card using my computer's copier. This allowed me to keep the original (for a card, perhaps?), but have the image for the bookmarks (thus the reason my two images look exactly the same on both bookmarks).
The designer papers, as well as the cardstock that I've used, have all come from the scrap bin. I've also used two different Spellbinder shapes to cut out the images. I wanted to mat my images once cut, but the next size die in each of the Spellbinder nestabilities that I used were too large, so I simply traced around the same die that I used to cut the image and hand cut the mats. I've used two different Martha Stewart punches to create the borders at the bottom of each bookmark.
You really can make these as simple or as fancy as you'd like. The shape and style of the bookmarks lend themselves to quite a lot of flexibility when it comes to decorating them, and of course, any of the little Inky Impression stamps would look adorable. I hope I've inspired you to have a go at making a few of these yourself -- and if you do, I'd love to see what you do, so please drop me an email with a picture or a link (firstname.lastname@example.org).