No, no, no, set down the caustic drain opener and walk away.
Instead, if you have a clogged drain, pour 1/2 cup of baking soda and 1/2 cup of vinegar down the drain and then let it sit for 15 minutes. Next, flush with boiling water.
You can help keep drains clear by flushing drains weekly with boiling water. You can also use small screens and strainers (like this Sink & Tub Strainer) that will help keep hair and other debris out in the first place.
03.27.07: We just read that you shouldn't pour boiling water down the drain if you have PVC pipes. Hot tap water is suggested instead.