Monitoring blocking queries in SQL Server 2012
The Microsoft Tiger Team has posted a set of scripts that handle this for you. Check this link out

https://github.com/Microsoft/tigertoolbox/blob/master/Running-Blocked-Processes/view_Running_Blocked_processes.sql

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. 

https://github.com/Microsoft/tigertoolbox