I start my plans with choosing color and recipient first. The primary colors, number and value, affect the pattern you choose. For instance, if your color choices can be sorted into darks and lights, you will need a pattern that looks good with high contrast colors, such as Log Cabin. If you will have three main colors, you will need a different pattern. If your colors are all of the same value, you will need an all-over pattern designed for low contrast.
The intended recipient also affects the pattern. Contemporary or traditional, young or old, simple or complicated pattern, etc.
I'm in the middle of this process right now. I am making quilts for my six nieces, who are all in their twenties. I want their quilts to be very different and unique to the person.
They have given me their color choices, and I will make controlled color scrappy quilts. Two of them, who happen to be sisters, selected browns and creams, so I chose two very different patterns that were suitable for two high-contrast colors. To make them interesting, I have bought many, many browns- I'm up to 55 now. Finding enough creams has been more of a challenge.
I have two nieces that are artists. Their quilts are the biggest challenge for me. Surprisingly, they weren't as specific about colors because they think like artists, not decorators, about color. One named all the colors she loved, which are most of them, and the other said "soft" colors (She lives in a cabin in the Maine woods-- so I keep seeing something different in my mind!). Doubly challenging because they live thousands of miles away and I have never seen their homes!
The fifth and sixth nieces gave me three colors; current decorating trends, so I have chosen modern fabrics. I had many more choices in patterns for three main colors.
When I'm fabric shopping, I see color, contrast, density of pattern, geometric/floral before manufacturer, designer, or theme.