Lessons I've learned the hard way in 25 years of home ownership. In no particular order.
Before you leave for a long trip, fill a big sink with warm water then let it all flow out at once. This will help flush your house's line into the main sewer before it gets a chance to set up and harden as it dries out while you're gone and not running water frequently. With low flow toilets and front loader washers, a big burst of water is something your pipes could be lacking.
If you have to plunge or otherwise treat a clog, run the hot water for five minutes after it. You want that sucker to make it all the way to your city's main line before it slows down.
DO NOT run onion skins down the garbage disposal. Just don't. Bad. Likewise large amounts of leftover rice. That stuff won't even get past the u bend.
DO NOT put fats or oil down the drain. If you have a super greasy pan, wipe it out with a paper towel and toss it. Paper towels are really cheap and this helps not just you but your future muni tax bill. If you have lots of used oil, pour it into a jar, put the lid on it, and toss it in the trash.
Treat your sinks, tubs, and toilets monthly with an enzymatic drain treatment. Not only does this keep each drain flowing like liquid black hole sunshine, it keeps buildups from forming that can break loose and clog your house's line. Don't get the liquid version of the treatment. It's ridiculously expensive. You can get the granular kind online and get dozens of treatments in one container. You mix with warm water to activate it and then try not to use that drain for 12-24 hours. Totally worth it. Also great at treating super slow drains without caustics that are hard on an old house's plumbing and fixtures.
You know that sign at the gas station bathroom? It applies at home. Only toilet paper (and bodily stuff, obviously) should go in the toilet. So it should go without saying, but just in case:
NO wipes, even flushable. They are a lie. They don't actually break apart like toilet paper. Not only will they clog your sewer line, they are costing taxpayers millions in municipal expenses to clean them out of the sewer mains.
NO Tampons. They aren't really degradable either and worse yet the strings snag in the pipe and then everything builds up behind the snag.