There are a lot of sources for knitting charts for various motifs and patterns, but there are times when you just can't find the exact motif you're looking for to use on a particular project. Maybe the sort of design you want just isn't available, or the charts you can find are too big or too small for the project you're planning.
Whatever the reason, making your own knitting charts is relatively easy and a great way to make a knitting pattern that's all your own.
If you don't already have an idea of what sort of design you would like, now's the time to get inspired. Look at the knitting chart books you have, search online for knitting charts, or just think about the project you're working on and what kind of motif would look best on your project.
You can also just sketch out a design yourself if you're handy with a pencil. I'm not a big artist but there's a flower doodle that I've drawn on things since I was in high school that I always thought would be great on a sweater, for instance.
Another potential place to start is simple photographs. If you wanted to make a chart that looked like a real flower, for example, you could check out a gardening website to look for a picture to start from.
Once you have your source material, it's time to get to work on your chart. I generally use plain old graph paper and a pencil when I'm getting started on a design. You can also use knitter's graph paper, which has boxes that are rectangular rather than square and better mimics the shape of a knit stitch. This paper is often found in the back of books on knitting design, or you can make your own online.
For this example, I started with a silhouette thought to be of Jane Austen. I downloaded the image and printed it out. I started out by just putting X marks in boxes with the general shape of the design but found that I needed a little more guidance so I actually drew the silhouette on the graph paper and then marked with a X the outside edge of the design.
Because this chart was just for me, I only marked the outside edges and didn't put Xs in for all of the interior stitches that would be knit in the second color.