Place the router properly
Avoid hiding it inside furniture, next to appliances or in a corner. The more central and clear it is, the better it will distribute the signal.
Use cable where it matters
TVs, consoles, desktop computers or critical cameras work better by cable. They free up WiFi and gain stability.
Review old equipment
An old or poorly placed repeater can make the network worse. Sometimes it is better to replace it with access points or a properly installed WiFi mesh solution.