Every tanning bed is different. That is why, it's important to talk about the amount of minutes appropriate for your skin type with a professional at the salon. If you are an experienced tanner, it is still a good idea to consult someone. It might be a different bed, or the salon might have changed bulbs since the last time you visited.
Most importantly to avoid getting burned in the tanning bed...
Until you develop a base tan, you will want to keep a close eye on your sensitive areas to avoid getting burned in the tanning bed. This includes the face, breast and butt cheeks. These are the most common places that burn. I don't advise anyone to tan their face because it does cause premature aging. If you do decide to tan your face, there are special lotions formulated for just the face. Some have a very light SPF, so the face is less likely to burn. For your other sensitive areas, you might leave them expose to the bulbs for half of your tanning visit. Then cover them up with a towel during the first visit. Next visit increase the exposure and so forth. You don't want to use an outdoor SPF lotion for these areas because they are not formulated for the tanning bed. Another option is to use a tattoo stick on these areas for half of your session. After 3-5 sessions, depending on your skin type you should be able to fully expose these areas, without the threat of getting burned.
Once you've developed a base tan you should be out of harms way from a tanning bed burn. That is, unless you do something stupid like go over the time allowed, do two or more sessions in a day, or lay out in the sun the same day as your indoor tanning session. Please be aware that bronzers can give the illusion of a tan, but these do not protect your skin from a tanning bed burn the same as a real tan.
In the event that you have burned from the tanning bed or sun for that matter, you will have to heal then start the entire process over. It is best to under tan than over tan. You can always track your progress, and make adjustments as you go. Now you know the steps to avoid getting burned in the tanning bed to keep a healthy, glowing tan.