For indoor planting you will need to find a small space, such as a closet or spare bathroom, that can be closed off and independently ventilated. Ventilation can be as simple as leaving the door ajar, provided you are not using supplies which generate excessive heat, but it is best to have separate air intake/exhaust outtake.
The first step in preparing your grow space is establishing ventilation. You will want to set up air intake from an outside source, and an outtake vent that will push hot, stale air out and away from your grow room, preferably outside. This can be done quite simply using 4-6” PVC pipes, silicon caulking and fans from old computer towers.
The second step you’ll need to take is lining or painting the walls. In order to diffuse light and prevent hot spots, line the walls with either aluminum foil (with the matte side facing out), aluminised mylar, or paint the space bright white. Do not use mirrors as the glass will absorb heat, which is quite the opposite to the desired result. During this time you will also want to cover any cracks and windows.
Third, you’ll want to protect the flooring from spills and grime by laying down plastic sheeting. Ensure the electrical outlets you’ll be using can handle an adequate amount of voltage for the lamps you’ve chosen, and invest in a surge protector for the space. Make space for lamps and other electronics on a shelf to keep them off the ground and away from potential spills. While you are arranging your shelving area, consider leaving and additional space for things like plant food, spray bottles and other supplies, so that they’re always close at hand and not in the way.
Finally, you will need light. If you are starting plants indoors, to be transferred outdoors for flowering, a few shop lights will be adequate. You’ll want one cool white bulb and one warm white bulb to generate the most complete spectrum of light possible.