Stop clogs at the source
Fit strainers in sinks and showers, keep grease out of the kitchen sink and only flush toilet paper.
Skip the harsh chemicals
Chemical drain cleaners can damage older pipes and rarely clear a real blockage. A plunger or a hand auger is safer for small clogs.
When to call
Several drains backing up at once points to the main line. This is general information for a sample site, not professional advice.