Gas furnace troubleshooting! Most people do not have a clue about maintenance work on their furnace unit, and delivery system, or both the intake and exhaust tubing-metal or plastic. The below link should provide you with a good initial understanding of your gas heating unit. Some tips that may help would be to: (1) have a secondary off, and on switch for the motor at the top of your basement stairs, or if the furnace is not in the basement, about 10/15 feet away-idea is that if the furnace starts on fire outside of its compartment, you can shut it off with out getting to close to the burning unit with this secondary safety switch. (2) Be sure to clean out the air intake screens, and below the screens in the pipes-dust, feathers, and both dog and cat hair, and any other items that could be sucked in this area. Make sure that the vents are open, and not blocked off by rugs, or other objects. (3) Changing the gas filter is important, or buy a good sturdy re-cleanable type, and just clean, and then replace the same filter-for years possibly. Generally, do my own work-except for the electrical, that is one reason to call a professional for a back-up, and worth the money if the person, or shop is reliable-and are not into rip-offs.
http://hubpages.com/hub/Gas-Furnace-Troubleshooting

Lots of good info there DF,

I had a piece of paper (wiring schematic) get pulled into the blower housing. That made it off balance when it ran, vibrating the floor. I thought the bearings or mounting bolts had loosened. I had no idea what it was, but it was a new furnace and the installer looked and found it right away.

the pipes-dust, feathers, cat, and hair

that would be a big one to suck the cat in , LOL , sorry had to do it.

Hey pappy, should have read 'car hair'! But, you are closer to the truth than you may suspect-this way when it really rains, or wind blows heavy-or gets a little cold ... animals love to go under the house-crawl space, and rip open the plastic lined ducking to get warm-some actually, get into the warm pipes-cats, rats, and raccoons have so far been reported-down your way, if anything, you may get a small alligator-then at least, that will be good eating anyway, i.e., you eating him!