Lock table in db; need restart server

How could thoroughly investigate and manage settings for lock on the tables in the database?

Often happens to me that the server that has two bases, the first 150 GB, 180 GB of second, happens to one request lock entire database.
After that, a simple query can not be released, and the server must be restarted.
After that, the processing can be executed.
I guess that happens lock over the tables.

I wonder how I could explore and configure the base?
How to Prevent it?

I'm working on SQL Server 2012, with Windows Server 2012.

Thank you