Personally I'm not a fan of buying a pattern only to find 3 or 4 columns on an A4 size leaflet. The printing is very small and the rows are broken over 2,3 or more lines. When reading a new pattern I like to be able to read it straight across one line.
So with this in mind I set about writing down my designs.
I add plenty of step by step photos for assistance if, indeed, it's needed.
This is an example of how my patterns are set out:
This is worked in *Mock Cable Stitch*
Cast on 32sts using 4.5mm knitting needles.
1. P2 * Sl 1, K2, PSSO, P2* rep from *-* to end
2. K2 * P1 Yrn P1, K2* rep from *-* to end
3. P2 * K3, P2* rep from *-* to end
4. K2 * P3, K2* rep from *-* to end
Taken from *FAIRYTALE* baby blanket
Each patterns has clear details on how much yarn you will need and the size of needle preferred. Also a list of abbreviations at the start of the pattern so you can familiarise yourself with the stitches used.
I tend to use pretty basic stitches that knitters of all abilities will be able to have a really good go at.
More often than not I buy the yarn first and design around that, probably, like most knitters, I'm a bit of a yarnaholic!!