Assess the space. Consider the purposes of the area and who is using it. Floor cushions can be added to provide additional seating for children and younger adults, while older people normally prefer sitting on chairs. For more formal use, utilize more elegant designs in your decor, while for a casual setting, you can employ more whimsy.
Pick a color scheme. While you can and should experiment with mixing patterns and colors, there should be an underlying color connection between the items and especially with the cushions. Cushions tend to be a bit more expensive than pillows, so aim for more conservative choices. You are then free to add splashes of color in the pillows.
Purchase fabrics wisely. A wide variety of fabrics are available, so take into consideration your local climate. If you don't want to worry about rain, your cushions and pillows need to be suitable for outdoor use and can be left outside all year. Or consider a storage place where the pillows and cushions can remain clean and dry when not in use.