How to change the default port of SQL server ?

SQL Server listens on default port number 1433. Following table will provide details of other default ports being used by SQL Server

Used By
Default port for SQL Server connections
Port for the SQL Browser service. In essence, the browser service returns a list of instances and the ports they are listening on that reside on the host. It is mostly used to identify where named instances are listening
The default port for Mirroring

To change the default port follows the step below in contrast to SQL Server 2008

1. Click on Start button in Windows. 
2. Go to All Programs
3. Click Microsoft SQL Server 2008
4. Click Configuration Tools
4. Click SQL Server Configuration Mangaer
5. Click on SQL Native Client 10.0 Configuration 
6. Expand on Client Protocols
7. Double Click TCP/IP (Right click Select Properties) on TCP/IP

You will find Default Port 1433, change it accordingly.

After changing the port number it is necessary to restart the SQL Services to make the change take effect.

Ways to know the port being used by SQL Servers
(1) This CMD command give the ports with the corresponding application that are using it 

netstat -abn 

(2) In the SQL ERROR LOG  look for a line like below.

Server is listening on [ <ipv4> 1433].