When deciding to convert your garage into a workshop, it is important to decide if your garage will still be used to park your cars. The problem with trying to have cars and a workshop in the same garage is that the cars will take up a lot of the space, cutting back on usable workspace. Moreover, if you do much woodworking, the amount of sawdust that accumulates can also cause problems for your vehicles. If you want a garage workshop, consider adding a carport outside for your automobiles.
Add in insulation behind the walls as most garages are poorly, if at all, insulated. Insulation will help make your workspace more comfortable and enable the use of it throughout various seasons of the year. Depending on your climate, you may also want a window unit air conditioner. If the garage is attached to your house, and if you have an air conditioner that can handle the additional space, you can go through the attic and add in central air.
Install additional wall outlets for power. If you are not familiar with how to do this, hire an electrician for the wiring to avoid fire hazards in the future. Set your outlets high in the wall, above table workspace areas for easier access with power tools.
Clean the concrete floor of any stains left behind by cars. Although a concrete floor makes a fine workspace, you can also have someone put down a composite, epoxy floor, which will be less slippery and have a more professional look.
Build shelves and closets along one or more walls for storage. Also build in a good, solid worktable. Add pegboard to a section of wall for hanging those tools you will use the most often.
Add in overhead lighting. Mount units of fluorescent lighting on the ceiling to provide a long lasting light source for your work area.