have to monitor blocking queries in SQL Server 2012. How do we figure out which queries are the locked ones? Do I use the Activity Monitor? I want actual SQL statements.
Complementing to what @Chris suggested -
You should use sql agent alert and choose to either email you or log to a local database e.g. dbautility or dbaadmin (whatever you choose the name). This script from Andy Mallon is a great resource (and an article about it here).
The Microsoft Tiger Team has posted a set of scripts that handle this for you. Check this link out
This will give you a lot of information about the processes running on your system. You can modify this to send the data to a table if that helps you track issues and do some trending.
Check out the rest of the scripts in the toolbox they have published.