Growing cannabis indoors require creating as close as possible a copy of its natural environment. While most people know that they have to take care about the temperature and humidity, it is often forgotten, that soil matters greatly too.
Cannabis plants are called weed for a reason - they can grow virtually anywhere and in their natural conditions they can be found in most surprising locations. These, however, do not always produce the top quality marijuana. If you have your eye on the crop, not on the pleasure of seeing the plant grow itself, make sure you put your seeds in a proper soil.
Never re-use soil found in some old pots around the house, or one from your garden. They usually host a number of pests that will make your cultivation a nightmare. Always use prepackaged, high quality soil and exchange it after every growing cycle. Saving on soil is a terrible investment, as it creates significant problems throughout the whole growing cycle.
Your mix should be light, allowing the plant to breath easily, drain the excess water (otherwise the plant can get suffocated) and provide it with necessary nutrients. Remember that it will be host to your favourite plant's most sensitive part - its root system. Make sure that it is comfortable and you will be rewarded!