Very difficult. If there's one thing about cats, it's that they don't like being pushed around. When a cat is on your bed and is comfortable, chances are it will stay there. This can be a problem if it's 11 o'clock at night and you want to get some sleep. You then enter your room to find a large, non-declawed male "kitty" on the bed (such as my cat Biggs).
Attempts to talk to the cat usually prove fruitless, being that most cats don't understand human language, or at the very least, choose to ignore it. You can try to
gently prod the cat, but if the cat is particularly comfortable, it will merely assume you are trying to pet it, and will flop onto its side, now even more relaxed.
Picking up the cat is also useless. When the cat feels your hands lifting him up, he will resist this attempt to remove him from the bed by digging all of his claws into the blanket. It is not recommended to try to unhook said claws, as they are usually quite sharp. Remember, if the cat wants to lie on the bed, he will fight with all his might to do so.
A solution that does work is to obtain a container of cat treats. Cats are powerless to resist the icky fish smell emanating from the plastic cylinder in which the treats are kept. Shaking the cylinder and letting all the treats bounce around and make noise also entices the cat. Bring the container close to the cat's nose, then retreat. Slowly make your way out of the room, holding the container. The cat, mesmerized by the scent and your shaking, will follow you out of the room. Once the cat is out of the room, drop a single treat in front of the cat, and while he is eating, run back into the room and close the door.
At this point you must remember, don't open the door. If you do, you will suddenly find the cat back on the bed again.