There are ways to tie a belt so it acts as a lock. If you have a lever-style handle, simply wind the belt around the handle, and then attach the other end to a solid object.
To secure your door, break a fork in half and put the sharp top section in the latch. Shut the door and push the bottom section of the fork in between the tines in the latch.
This simple rope hack will help you to feel more secure. Tie one end of the rope tightly to the door handle, and then attach the other half to a sturdy object.
You can use a door wedge to stop a door that opens inwards from being forced open. Simply take your wedge of choice, and jam it as tightly as you can beneath the door.
To use a chair as a door barricade, push it against the door as close as you can get it, and tilt it under the door knob or handle. Ensure that the chair feels secure.