Need Trigger to auto fill insert from data in another table

[Paul Littrell]

I am attempting to use triggers to auto populate 3 fields when a record is created. I have one table {table1} with 4 fields user_id(key field), user_name, department,manager. What I would like to happen is when a record is added to {table2} which will only have the user_id in the record, to pull the name, department, and manager from {table1}.
I cannot seem to figure out if this is possible using triggers, or the syntax if it is. Has anyone done this? And if so, could share the syntax with me?

Thank you,
Paul Littrell