Locate wall studs with a stud finder
Mark the stud locations on the wall
Move the bookshelf into position
Level the bookshelf
Mark anchor points through the bookshelf or mounting brackets
Drill pilot holes into the studs
Insert appropriate screws or wall anchors
Secure the bookshelf to the wall with brackets or anti-tip straps
Tighten all fasteners firmly
Recheck that the bookshelf is level and stable
Load books and items evenly
Reinspect the fasteners periodically