Personally speaking, I feel that the only real requirement is that the pastor who is about to give communion read Scripture about communion, i.e. the seriousness of the matter. Then unless the pastor/elders know of people who shouldn't participate they are free to serve communion to all those who want to participate.
In the case where the pastor or elders know of someone who should not participate, they should privately (if possible) before entering into communion, ask the person to not participate.

Tom