The most detailed instruction we have regarding how to observe communion is in

1 Cor 11:23-26

For I received from the Lord that which I also delivered to you, that the Lord Jesus in the night in which He was betrayed took bread; and when He had given thanks, He broke it and said, "This is My body, which is for you; do this in remembrance of Me."  

In the same way He took  the cup also after supper, saying, "This cup is the new covenant in My blood; do this, as often as you drink it, in remembrance of Me."  For as often as you eat this bread and drink the cup, you proclaim the Lord's death until He comes.

As you can see, there is no command regarding the frequency of the observance, and very few details of exactly how to share communion. We do not believe that it happens whenever we eat together. There should be a giving of thanks specifically for the bread and for the cup, and both are taken in rememberance of Jesus' sacrifice.