1. Get a sketchbook or bind together a stack of paper.
Flip books work best when they're small, but thick; a flimsy flip book won't let you get a good grip on the pages to flip them properly enough. A large flip book will move too slowly as the pages encounter air resistance. You'll want to get a pocket sketchbook, 3"x5" or so, maybe a little bigger, maybe a little smaller. For the best effect, you'll want something with a flexible top cover, but a rigid backing - and pages with a slightly lighter paper weight so you can see one through the next. Nothing as thin as tracing paper, though; tracing paper is hard to flip because it's so light. You can also just bind together copy paper at one end. Trim it down to size, and either glue the ends together, clip them, or staple them with an industrial-strength stapler. You'll want more pages than you actually intend to use for your flip book animation.
2. Create your first drawing on the bottom of the stack.
Flip books work best when you flip them from bottom to top, using your thumb to fan the pages, so you want to start your first frame at the bottom and work in reverse order. Your first drawing should be the start of your sequence; flip books aren't usually drawn the way most animations are, using keyframes and in-betweens, though if you want to try putting key drawings in at set intervals on different pages, you can. It might not work out the way you want, though. The point of the flip book is to exhibit basic animation skill and principles. I suggest working in pencil so you can erase. Also, try to draw closer to the bottom of the page, in the space covering the bottom half. Anything close to the top half / binding may be harder to see when you're flipping.
3. Layer the second to last page over your first drawing and draw the next frame.
This is the real test of your ability - or good practice if you're seeking to hone it. Remember, this is not the default animation process, but it's a good exercise to practice estimating frames. You'll be able to trace this somewhat, if you're using sequential motion; some people just create flip books of random sequences of related images. What you'll want to do is deviate just enough in your drawing to demonstrate one frame's worth of motion. If you're animating a blink, you may want to draw the eye one-third closed, etc. The timing doesn't have to be perfect for a flip book, but you'll find the more you practice, the better you'll get. Some people do flip books entirely of stick figures just for the practice.
4. Continue layering and drawing pages until your sequence is finished.
It's basically rinse and repeat from here. Animate from beginning to end, but with the pages in reverse order from bottom to top. Have fun with it. Be crazy. Draw stick figures, draw details, blow up an entire stick army with little pencil-sketched smoke clouds. Do whatever you want, until you feel like you've hit the end point. Because this is just a basic flip book, you don't need to ink it, though you can if you want to prevent it from fading.
5. Flip your book to watch the animation.
With larger flip books, you can just lift the pages, then let them fall. With smaller ones, you can brace them against your palm and use your thumb to fan through the pages quickly, and watch your flip book animation fly by.