How To Draw A Entity-relationship Diagram Of A Hotel?

first begin to analysis the er diagram for the hotel:

then start to think about the type of system u want to chose the entities
er diagram can be for management system or reservation system or .....

if reservation system the hotel will have 3 basic tables and you can add more .....

1- guests = pasportno + tel + email + .....

2- room = roomno + size + cost + .....

3- reservation = Reserveno + check in + check out + total cost + .....

and you can add more entities like facilities ,..........

finally start to analysis the relationship between entities

1-  (guest - reserve)  (1 - m )
  guest can have many reserve but reserve no back to one guest

2- (reserve - room) (1 - m)
   reserve can have more than one room but the room back to one reserve

by adding more entities you can add more relation between entities     
hope that will help you in your problem