Basic Queries to troubleshoot Database Mirroring

Check the state of the DB Mirroring using DMV sys.tcp_endpoints

select name,type_desc,state_desc,port,is_dynamic_port,ip_address 
FROM sys.tcp_endpoints

Check the DB Mirror information using DMV sys.database_mirroring:

select database_id,mirroring_state_desc,mirroring_role_desc,
mirroring_partner_name,mirroring_partner_instance 
from sys.database_mirroring

Thanks!!!