Install the laminate flooring in each separate room per manufacturer's directions. Bring the laminate flooring all the way up to the doorway so there's a gap less than an inch wide between the two floors.
Choose a transition molding for the space between the two rooms of laminate flooring. If the floors are the same height, a T-molding will work best. Purchase a step-down transition for floors that are two different levels. The bottom part of the transition that touches the sub floor should have a ¼-inch expansion gap on either side of it.
Measure the doorway with a measuring tape. Transfer the measurement to the T-molding or step-down transition with a pencil. Cut the transition with a miter saw.
Vacuum the gap between the two laminate floors.
Spread polyurethane glue on the bottom of the T-molding or step-down transition. Press the transition into place over the two laminate floors.
Allow the polyurethane glue to dry overnight before walking on the transition.