When you spend time out in the sunshine, tan lines are expected, but when you are in a tanning bed, it seems like the chances of tan lines are slim. Since each long bulb in a tanning bed creates its own light source, it's possible to come out striped like a zebra.
Take off all of your clothing and jewelry that could block UV light from shining on your skin.
Apply your tanning lotion or oil evenly all over your body and rub into the skin well. There are several products on the market that claim to give you a darker, more even tan, but a simple tanning oil will have a similar effect for a much smaller price.
Apply your protective eye wear, and if you have long hair, pull it back so it won't block the light from your shoulders or neck (see Reference 2).
Lay in the tanning bed flat with your arms away from your sides and your legs shoulder-distance apart. Once you start the tanning bed, be sure to alternate your position and shift from side to side, roll onto your sides and back, and put your arms over your head to expose under your arms every few minutes so that the coverage is even and you don't step out with long stripes from the individual bulbs.
Apply a light moisturizing lotion once your tanning session has ended. This will help to keep your skin from getting dry and keeping your tan even.