After the Kayak, choosing a paddle that suits your physique and paddling style is the most important decision you'll make. There are a lot of choices depending on what you're looking for.
LENGTH
The first factor you to consider is the shaft length which depends on your height and the kayak width. In general, the taller you are and the wider the kayak, the longer the shaft should be. The chart below from Werner Paddles gives an idea of how to choose your shaft size
Paddler Height | Boat Width | |||
< 23in | 23in to 28in | 28in to 32in | 32in | |
< 5ft | 210cm | 220cm | 230cm | 240cm |
5ft to 5.5ft | 215cm | 220cm | 230cm | 240cm |
5.5ft to 6ft | 220cm | 220cm | 230cm | 250cm |
>6ft | 220cm | 230cm | 240cm | 250cm |
Note that these numbers aren't set in stone. I for example am 6 feet tall and my kayak is only 20.5 inches wide, but I like to have a short 200cm paddle for when I paddle up wind, and a long 220cm paddle for when I go down wind, so I will alternate between them depending on what the conditions for the day will be. If you are a high angle paddler, you would probably want to decrease the lengths above by about 5 to 10cm.
The video below from Canterbury Paddles tells how to set the right paddle length for you.
LOW VS HIGH ANGLE PADDLER
MATERIALS
BLADE DESIGN
SHAFT DESIGN