STEP 1: Enabling TCP/IP
First we must tell SQL Server to listen on TCP/IP, to do this
perform the following steps:
1. Launch the SQL Server Configuration Manager from the "Microsoft SQL
Server 2008 R2 > Configuration Tools" Program menu
2. Click on the "Protocols for your SQL instance"
3. Right click on "TCP/IP" in the list of Protocols and choose, "Enable"
STEP 2: SQL Browser Service
Next, we have to determine if we want the SQL Browser service to be running or not. The benefit of having this service run is that users connecting remotely do not have to specify the port in the connection string.
STEP 3: Firewall..?
At this point you should be able to remotely connect. If you still
can't chances are you have a firewall configured on the computer where SQL
Server is running.
Make sure to add the port number you used for tcp/ip connection added to the exceptions list. The default port for SQL Server is 1433 unless you changed it to listen on another port
If you chose to use the SQL Browser service, you must also add
sqlbrowser service executable to the exceptions list as it listens on udp