I would speak to the general education teacher first and explain the importance and benefits of maintstreaming. I would then ask permission to speak with the students in the gen ed classroom and discuss the importance of acceptance, as well as how students with special needs may have ways of learning that differ from their own. Allow students to ask questions and discuss their present or past interactions with peers or family members with special needs. After doing so, ask for student volunteers to assist students while being mainstreamed, as well as play with them at recess or eat lunch with them. This approach has worked very well for me.