Use proper topology/geometry for intended application; i.e., microstrip and/or stripline.

Use optimal stackup, depending on application and number of nets to route. Locate all signals routing planes adjacent to a solid reference plane, if possible.

On two-layer boards, route power and ground traces radially and very close one of other.

Locate components based on radial migration from highest to lowest bandwidth.

Make power planes physically smaller than the ground planes per the 20H rule.

Always locate a signal routing layer adjacent to a solid reference (image) plane.

Never violate an image plane with a signal trace. Moats are acceptable in an image plane, provided the adjacent signal routing layer does not have traces cross the moated area.

Never place three or more routing layers adjacent to each other. Each routing layer must be adjacent to a solid reference plane.

Partition the printed circuit board into functional subsections. Separate high-bandwidth areas. Isolate each section using partition or moats, if required.