The first thing to know when planning a trip to Carlsbad Caverns National Park in southeast New Mexico is that the ranger guided tours will not be available if you have not booked in advance. It is important to plan your visit by going to the National Park system website www.nps.gov first where you can buy tickets for the tours well in advance of your arrival. If you are not able to secure tickets in advance, you can still do the self guided tour which allows access to part of the main area and the natural entrance which is a paved path from the visitor center to the bottom.
If you elect not to take the hour plus walk to the bottom, you can ride the elevators which take less than a minute. Upon arrival at the bottom, you will find yourself at the limited snack and souvenir area. If you visited many years ago you may recall being able to get all sorts of burgers, hot dogs and such. Now you can only get things like packaged muffins and bottled drinks which may not leave the small concession area. This is due to the effort to curtail trash and food smells in the cavern which could attract insects and animals to get into parts of the cave where they have not been before. As such, be sure to get your food and drink situation taken care of before heading to the bottom.
If you want to see the bats, be sure and plan your trip after they arrive in May and before they leave in October. The bats winter in Mexico where it is warmer.