Start with geometry
A centrally located access point usually reduces average distance to clients. Placing the only router at one extreme of a long home forces radio signals through more walls to reach the far side.
Building materials matter
Masonry, concrete, metal-backed insulation, appliances, mirrors and dense utility spaces can attenuate or reflect radio energy more strongly than light interior partitions.
Avoid hiding the access point
Putting a router on the floor, inside a metal cabinet or behind dense electronics can make a hard radio problem even harder. Follow the manufacturer's intended orientation and ventilation guidance.
The client is part of the link
A powerful router cannot compensate indefinitely for a weak client transmitter or small antenna. If a phone cannot send a usable signal back, strong-looking downlink coverage alone is not enough.
More access points can be better than more power
For larger or radio-difficult homes, additional well-placed access points or mesh nodes are often more effective than trying to cover everything from one corner.