Measure the space where the bookshelf will go
Decide the bookshelf height, width, and depth
Choose the material, such as wood, plywood, or MDF
Gather tools, including saw, drill, screws, measuring tape, level, sandpaper, and clamps
Cut the side panels, top panel, bottom panel, shelves, and back panel to size
Sand all cut edges and surfaces
Mark shelf positions on the side panels
Drill pilot holes for shelf supports or screws
Attach the top, bottom, and side panels together
Install the shelves at the marked positions
Attach the back panel
Check that the bookshelf is square and level
Secure all joints with screws, nails, or wood glue
Fill holes and gaps with wood filler
Sand the filled areas smooth
Paint, stain, or varnish the bookshelf
Let the finish dry completely
Anchor the bookshelf to the wall if needed
Place books on the shelves