Another method of maintaining clog-free drains is to periodically pour a pot of boiling water down the drain.  You can even use recycled water; everytime I make spaghetti I pick a different drain and after draining the pasta I pour the water down. The water is hot enough to kill most of the bacterial mats that hold the clogs together.

You're going to have a heck of a time getting a snake down the drain. Not only do many standard drain "crosses" prevent a snake from maneuvering well, if at all, but the pipe has a sharp bend almost immediately after the opening. A better, if slightly more involved, method is to remove the bathtub overflow cover. Remove the cover, stopper linkage, and stopper - it's all connected (often, the stopper has become a bucket for icky muck, which might be the root of your problem). Run the snake in from there instead of the drain, and you may save yourself some unecessary sweating and swearing. I wish I had known that about a year earlier. :)

When we had stopped drains, a neighbor suggested DrainCare which apparently works by "enzymatic action."  It seemed to clear our drains.

You let it sit in the drains for several hours without running water.

Does anybody have experience with these "enzymatic build-up removers?"

It's from Enforcer Products (ominous name).  

I wopuld really like to read your answer, so why the hell do you put it in grey and small. I am sure that I am not the only one that can not read it. I notice that  "post Comment" is written in a good size and a readable color.

I have found the easiest way to unclog bathtub drains is to use the toilet plunger. This works easily, and use it before the tub is totally stopped up. When the tub begins to drain slowly, plunge away, and it will soon gush out.
Of course, this is much easier than going under the house and disconnecting the pipes and cutting out tree roots that have grown into your drain pipe. I have done that too, and it wasn't fun at all. So I keep plunging as needed (usually soon after my grown children come home to visit.)

You all are making too much work out of this. These two drains are usually clogged by hair and lint and the slim that starts to grow on it. Remove the covers, grab a flashlight and use a small piece of wire (coathanger size)with a little hook on the end, or a hemostat, and just reach in and start removing the gunk. Place it on a paper towel that is nearby and throw away. You don't need any chemicals or mixes for these drains....usually. This method does put you close to your gunk, but it does work.

The baking soda/vinegar trick is terrific, but tends to work far better (and make it less likely you will need the snake) if you first plug up the overflow holes you often find in sinks and bathtubs (which also allow air into the drains) and follow the vinegar chaser with a kettle full of boiling water. Just be sure to wait until the fizzing has stopped before pouring the water.

I like to use the outside hose and blast away my troubles.  It has worked very well in the bath tub and laundry sink.