Tobacco plants need to be exposed to full sun while growing. Tobacco roots grow quickly and often close to the surface. Be careful around plants when hoeing or cultivating around them. Try not to disturb the soil anymore than necessary. As the plant begins growing, remove all suckers as they will sap the plants growth.
Tobacco plants suffer from several diseases and are attacked by several leaf chewers.
I recommend using sevin dust to control insects. Be cautious not to use any form of systemic insecticide that will penetrate the leaf. Remember, you may be chewing or smoking this plant and you do not want to be ingesting chemical residues. A catalog is available for download in a self executing zip file.