First of all, decide where you will install each shelf and measure the height that you assume for each of them. Mark the height with a pencil; then, with the help of a 1-meter level, put another pencil mark on the wall across the length of the shelf. It would be enough to install brackets at both ends and every 60 centimeters along the shelf. Use the level again and mark those places where you will locate the brackets.
While drilling the holes, a hammer drill or an electric drill will immensely facilitate the work. If you don’t already have one, you might consider borrowing one from your neighbors or renting it from a store near your home if they are expensive. After you arrange your drill bits and fasteners, hold the drill level and dig holes into all the spots you marked before.
Once you have drilled all the holes, start installing your mounting brackets onto the wall. The reinforced support steel brackets are the best options if you are looking for a budget-friendly mounting solid bracket. You can purchase them online as well as from home improvement stores or hardware stores in your neighborhood.
Place the first bracket on the wall, make sure the top is even and the mounting holes match the drilled holes. Place the fastener through the hole into the wall and finally place the nail or the screw with the help of a hammer or a screwdriver, accordingly. Follow these steps for all the brackets and check if they are level with each other after installing each one of them.
When you have placed all the brackets, prepare your shelf or shelves. Depending on your DIY skills, you can either buy shelves from hardware stores that are already cut and laminated, or you can cut a shelf board from certain materials such as sheathing or plywood. After making the necessary measurements, cut your shelf to length and width with the help of a table saw or a circular saw. As the final step, remove the jagged edges and splinters using low grit sandpaper.
Also you can look How to Style a Bookcase