Use your imagination and pre-plan. Treat closets like small rooms. DO NOT stand in front of them. Clear them carefully. Look behind boxes and clothing.
Stairways pose threats as well.
There are many techniques for stair clearings. Choose a simple technique and move only under the cover of your search team. When you reach a danger area, stop and allow your partner to move up and cover you, while you clear. Hallways can be complex. There are usually many doorways and exits in the hall.