Look at the different shapes of foam pillows. Some are contoured, meaning they have a special shape that can offer a different type of support. The top and bottom portion of the contoured foam pillow are slightly raised. The other option is a foam pillow shaped like a standard pillow.
Check the density of the foam pillows you're considering. The higher the density, the firmer the pillow. Generally, foam pillows will have a density between 3 and 6 lbs. with 3 lbs. being the softest and 6 lbs. being the firmest option.
Test out the foam pillow. Many mattress and furniture stores will have foam pillows set up just like they do mattresses. Lie down on a mattress with the foam pillow in your normal sleeping position. This will give you an idea of which shape and density level is right for you.
Use the foam pillow a few nights before making a final decision. This involves finding out the retailer's return policy. You might find that you need a different shape or a different density after sleeping on the foam pillow you chose for a few nights.