I used to tan all the time. I would stop for a long time and then start up again. If you have never been in a tanning bed, take it easy at first because the tanning beds can be a lot different then natural sunlight. Depending on the tanning bed, your results may vary. There are different levels of uv bulbs used in tanning salons. Usually you can go into a tanning salon, explain to them that you have never tanned before, and they can look at your skin and tell you how long to start out with. If you do ok, then increase the length of time you are in the bed a little at a time. You can also start going more often. When I start out from no tan, I go for shorter time periods like 10 minutes twice a week. Then step it up to 15 to 20 minutes and go once a week. That does really well for me. But again, everyone is different.
Be sure to get some good lotion made for tanning beds. They should have some at the salon. It will help you have a better tan and prevent burning. I usually buy the ones that have skin bronzer in it to help give some added color.
Another bit of advice is to rotate in the bed if possible. Alternate from your back to your stomach. This will help keep your body evenly tanned and can also help if you feel like your back is getting too hot.
As for the spray on tan, I have tried those a couple times. They are nice and definately safer, but they rub off your skin if you rub too hard or wash too much and I think they make you smell wierd. I tried a couple different salons for that and the tan only lasted about a week before I started to have areas fade. It wouldn't hurt for you to try that out to see if you like it though. I know some people love it. One other bad thing about this though, is that when you go out in the real sun your body won't be ready for it and you will burn.
Have fun!