With lotions, you get what you pay for. Start off in a low pressure lay down bed for half of the normal time (so stay in for 10 minutes instead of 20). This is assuming that you're as pasty white as I once was.
Work your way up from 10 to 12, to 14, 16, 18, then 20. Don't be afraid to drop down a level, or to stay on the same level for as long as you need to while your skin adjusts. As for lotions, I recommend California Tan's Step 1 products. They are made specifically for the beginning tanner who is working on his "base tan" - which is what you're doing. I've shopped around and found that
www.waycheaper.com has the best prices (I used to go with eBay but about 1/2 of the lotions on there are discontinued, old, and not very good). In particular, I would recommend you buy CalTan's C1FX w/ Bronzer.
After a few months (don't expect to get golden brown after the first few visits!) you may want to reconsider your package and buy a few months of high pressure standup sessions. If you have any more questions, feel free to post them here and I'll get to them ASAP.