To avoid bugs be sure to use sterilized soil and containers and don't bring other plants from outside into your growing room. If you have bets, ensure that they stay out of your growing room, since they can bring in pests on their marijuana seeds. Examine your plants regularly for signs of insects, spots, holes in the leaves, browning of the tips of the leaves, and droopy branches. If you find that somehow in spite of all your precautions you have a plant room full of bugs, you'll have to spray your plants with some kind of insecticide. You'll want to use something that will kill the bugs and not you. Spider mites are probably the bug that will do the most damage to the marijuana plants.