Cover the floor of the area where you want to expose the beams. Use a drop cloth over the entire flooring area, and tape the cloth to the walls at the edges for full coverage.
Tear down the ceiling in the room. If you have a standard plaster ceiling, punch a crowbar or large hammer up into the plaster and start prying the plaster away, allowing the plaster bits to fall to the drop cloth. If you have a tiled ceiling, pry off the tiles first, and then remove the plaster.
Inspect the ceiling area once you have the entire ceiling torn down to determine how to proceed. If the ceiling beams are completely exposed all the way to the roof, the interior of that roof will most likely be wood. If the ceiling beams are beneath an attic, there will be a subfloor that connects the beams together.
Restore the beams. If the beams appear in good condition, apply any standard stain to return the beams to their best condition. If the beams are discolored, apply a wood stripper to the beams to remove the outer layer of wood and reveal the untouched wood beneath before staining.
Fix any problem areas around the newly exposed beams. You can restore the inside of a roof or the wood subfloor of the attic in the same way you restored the beams. If you prefer, you can also paint the wood subfloor between the beams or tile between them.