As a fellow DIYer, we all love the idea of working on projects at home. Maybe just attempt to save money, or even just to have some self pride that you can take care of things on your own. Plumbing is of course the forefront of potential DIY issues that you work on. We need and use plumbing items constantly, so it's only natural that they would have to be maintained and/or repaired.
Step one, always know where the main water shutoff is. Seems pretty self explanatory, but it's essential to know the location in case there is an emergency and your house is flooding. Locate the individual cutt-off valves as well. This will help when you're doing small repairs to toilets or sinks. And make sure you have an emergency number always ready.
Keep your toilets free of "other" debris. Sure, if you're a parent...this can be a difficult task to avoid Barbie taking a swim. The point is to try to keep larger items such as paper towels, hygiene products, food and other things from being flushed. If you can reach it from the bottom of your toilet, you could be in for a bad issue. This goes for your other drains as well. If it's not intended to go down a pipe...keep it that way for good.
Know your water heater, know if it electric or gas, and know how to shut it off. Check all pipes associated with the water heater on a regular basis. There should be some sort of drip pan already available, and if there isn't, get one. 10 years is about the average life span of a water heater, so keep that in mind depending on when you moved or built your home.
It's also worth considering having additional parts on hand. Even things that you can go ahead and reinstall like a toilet seat, sink stopper, or a shower head.
For those that don't want to attempt the project, or maybe you just moved into a new home, the first good piece of advice would be to just schedule a professional plumbing inspection. You may not have any current issues, but an inspection will give you an idea of what may be coming.