Thanksgiving acknowledges God's goodness to us. Thanksgiving is important in the Christian life. As we thank God for things, we put those things into the context of our relationship with God. In Supplication we ask God for what we need. In worship, this supplication normally includes the needs of the congregation, nation, and world.
Intercession is a specific kind of request, directed towards the needs of others.
Through intercession we bear each other's burderns, and join the other members of the community in putting their requests before God. The one aspect of worship which is most specific to Christianity is the sacraments. This is also the element that is the most dangerous to describe in a document such as this, which is intended to describe Christianity in general. That's because the definition of sacrament is somewhat different among different groups. For Protestant theologians, this must be connected with a specific promise of God, as recorded in Scripture.