Can you please list the most common ideas a school can do to welcome deaf children, and help them fit in?

Different? Hi-what a thoughtful question. The answer does depend on the age of the class. I am going to guess elementary, helping to define hearing loss for themselves. Earmuffs, etc. Or a movie with no sound; so they "know' what it is like not to hear. Read short biographies of people with hearing loss who have excelled in their own way; the class could study sign language and "reading lips"; more. Luck.
Signing classes. Lots of visual signage and information to read, visually stimulating environment, and the idea of teachers, assistants and even other children having the option of learning to sign - and even involving the deaf children in the teaching / learning process- I thing would be very helpful.