Table1 has two columns col1 & col2. I have added 4 columns to one of the tables .the new columns added are user_inserted, date_inserted, user_modified & date_modified.

this is specification for trigger :
I need to insert user_inserted & date_inserted column values with current date when there is an insert on table. And I need to insert user_modified & date_modified values when there is update.

How can I code this trigger/triggers in best way performance-wise.

Thanks In Advance.