The process which is relatively simple and employ, occasionally makes use of over the counter cold medication since it contains a key ingredient - ephedrine. In the latter distillation parts of the process, flammable solvents such as ether and acetone are used to extract the meth from solution, and its quite common for the "home-made meth labs" to explode.
So if you notice a particular chemical smell when entering a hotel room, make sure you don't stick around for the coffee, you may be in for a surprise.