What your design proposal should contain varies depending on what publication you're submitting it to. Some publications ask for the entire pattern and finished sample or photos, while most just want an idea of your design (presented through a sketch, swatch, and descriptions). Knitty has a detailed submission guide discussing everything they'd like you to include in your proposals, and Interweave recently released a template to fill out that shows everything they want to see in a knitting submission (click here, scroll down to the bottom of "Useful Documents"). These resources are worth taking a look at no matter what magazine you're submitting to (note that Knitty asks for the entire pattern up front, whereas Interweave just wants an idea of your design).
But if your chosen publication doesn't have such detailed submission information, it might be helpful to take a look at one of my accepted design proposals and see what I think are important elements to include. See those red numbers? I'll be talking about those in a bit more detail below.
2. Sketch! This doesn't have to be a work of art, but should convey the overall look and fit of the piece.
3. Swatch. This should feature the stitch pattern(s) of the final piece and any other details such as a unique edging, embroidery, etc, using a yarn similar to that you envision the the sample worked up in.
4. Description. I don't always even put this in, but it can be nice to talk a little bit about the inspiration for the piece, what makes in unique, why knitters would want to make it, and/or how it fits into the magazine's themes.
5. Yarn info. List what yarn you used in the swatch and what characteristics and fibers would work best in this piece (does it need elasticity, such as from wool? would it work best in a solid, semi-solid or variegated colorway? what weight should it be? etc.). If the publication provides yarn support give a few ideas of specific yarns that would fit the bill. It's also good to keep in mind what types of yarns the publication generally uses; inexpensive yarns, luxury yarns, yarns available in a different country, etc.
6. Here I include a list of notions required for the piece, as well as the needles I used in the swatch.
7. Construction details! Tell them how it's made. Is it worked top-down or bottom up? In the round or flat? In pieces or seamlessly? Don't be afraid to go into detail here. I find it helpful to make a bullet-pointed list.
8. What size(s) is it going to be? And if it's a wearable item, it would be a good idea to point out what size person it would fit (for example women's medium).
9. If you haven't worked with this publication before, it's nice to write a little bit about yourself, particularly in regards to knitting experience. Things like, how long you've been knitting, if you have a blog, previous design work, or if you have expertise in a specific knitting technique.
10. And finally, your contact information. This is very important. Include your phone number, mailing address, and email at a minimum.
If you'd like to see a few more examples of other designer's accepted proposals, check out this Ravelry thread.
And that's it! I hope you found these posts on how to submit your knitting or crochet designs to a magazine helpful. If you have any questions do let me know!
P.S. If you're wondering what the design is that you see in the above submission, check out the patterns page! :)