Why we stand when we sing? 
II Chronicles 20:19  "And the Levites, of the children of the Kohathites , and of the choldren of Korhites, stood up to praise the LORD God of Israel with a loud voice on high." 

Why we clap our hands?
Psalm 47:1  "O clap your hands, all ye people; shout unto God with the voice of triumph."

Why we lift our hands?
Psalm 63:4; Psalm 134:2; I Tim. 2:8  "I will therefore that men pray every where, lifting up holy hands, without wrath and doubting. "

Why we have audible praise unto God?  
Psalm 103:1; 34:1; Acts 4:24 "I will bless the Lord at all times: his praise shall continually be in my mouth."

Why do  we  rejoice and get excited?  
Phil. 4:4, says,  Rejoice  in  the  Lord always and again I say, rejoice. Some people just get excited about what God has done in their lives.

Why do we dance?
Psalm 149:3, says, Let them praise His name in the dance…. 

Why do some people go to altar?
James 4:8, says, Draw near to God and He will draw near to you.   There  are  those  that  feel they are getting closer to God by coming to the altar to worship Him.