What maintenance practices are best to keep my kitchen sink drain open?

Never use a garbage disposal and always keep drain strainers in place and empty them as needed.

Never, ever, pour grease down the drain and you will more than likely not have a problem.

Use it as a sink. Don't try to use it as a garbage disposal. Problem solved. Every now and then some drain cleaner wouldn't hurt. But in general it shouldn't need much maintenance unless there is a problem.

Hard water can be a problem. But there isn't anything you can do about that except to install a water softening system.

If you feel that you need to run some hot soapy water down the drain. Flush with more hot water. That's it...unless you have a clog.

A big pot of boiling water straight off the stove an down the drain help clean out that drain. Bout once a month to every other. I pour the biggest pot we have down it