We teleconference all the time w/ potential candidates out of state. My interviews are preset. I test the individual on what I am hiring them for. I usually have about 20 questions we run down on the technical side of things, so that we are certain they know what they are doing when they are hired. You would not believe the crap ive seen on a resume that wasn't true.
Depending on his/her answers, we may proceed to the interests, goals, commitment of the individual if hired. If they are are just shining us on, it is usually a short tele interview.
No offense to the previous poster, but I would not spend time learning the products they sell. That will be taught to you if hired. You aren't expected to know that unless you have it anywhere on your resume or a hobbiest lawn guy.
Never bash any of your past employers. If asked about your past history, just bring up that you worked there and enjoyed the experiences you learned. Leave it at that.
Keep your answers short and direct. Do not ramble on and on, just to hear yourself talk, like you do on here.
Good luck.