If you have a companion, take turns being the landmark. One walks out to edge of vision, looks back and gets lined up on course by person who stayed behind. They then stay still while stay-behind leapfrogs them to edge of vision, repeat process.
Give the compass to the LAST person in the group. The rest of the group form a line in front of him. If this line deviates from compass course, the compass guy orders "LEFT" or "RIGHT" corrections by voice or whistle. This method works, but as always - it works best with practice and discipline.
Before GPS, this method was the ONLY way to have any hope whatsoever of maintaining a straight course with acceptable margin of error in total whiteout conditions, such as a blissard or dense fog.