Decide what you would like to have a personal piece of art from. For the most part, the ones I doodle with aren't my own, so make it fun and create something that means a bit to you. Not everyone has played Panic Restaurant out in the world, but if Cookie is your 8 bit trearued memory, then by gawd, draw yourself a Cookie. Today, for gits and shiggles, I am going to do Goldman from Dragon Quest. How do I obtain a good enough picture of Goldman to pull it off? Well, there are two ways to do it. I prefer to play the game on an emulator for a second and get it in the pose I want most of the time. If it is a boss at the end of the game and you just don't feel like plugging away for 30 hours to make it to Chaos, there are tons of great sprites sites like The Spriter's Resource out there to plunder.
Get yourself some graph/grid paper. I prefer 4x4 but 5x5 would suffice for a beginning, I just prefer the smaller style myself but you could be different.
After that, with a pencil (pencils are you new best friend), draw a line halfway through every line until each original box now has four boxes inside of it. Remember, the smaller the sprites you make, the better looking or else you'll find yourself admiring your handiwork most from 10 feet away and that can kind of suck.
Once that is done, pull up your sprite in the good old trusty Paint program that comes with every computer I have ever had and hit Ctl+G. Grid view is the secret folks. Zoom in to the max and there is your template in all its glory. I advise you strip the background away like was done here as it makes it tons easier. Unless it is something you want of course.
Also, do you see that tiny number on the toolbar at the bottom? 47x47px tells you exactly how many blocks you are going to need. Take my word for it, don't "quad-square" an entire sheet just for something like a 47x47 piece. Count out 47 squares vertically and 47 horizonally and only grid those up as anything else will be wasting a shitload of time.
OH YEAH BEFORE I FORGET, YOU NEED THE PATIENCE OF JOB BECAUSE THIS SHIT TAKES FORRRRRRRRRRREVER!!!