First thing to do before you plant a single seed is to line the closet with plastic. They also sell giant zippers at hardware stores for a complete seal. This will keep the smell from saturating wood, stud, drywall, etc. You'll never get that smell out otherwise. More importantly, this will allow you to determine where the air/smell goes when it leaves the closet. You don't want smell sneaking into some unseen gap, then coming out in your bedroom, etc.
Equally important is an intake and exhaust. They need some bends in them or other means to keep light from coming in or out. Ideally the exhaust will exit your house as high up as possible through the roof. If not, then keep it up as high as possible, and as far away from windows, neighbors, etc. You'll want a fan to exhaust the air, and not rely on gravity.
If there is still a strong odor, you may need to invest in a carbon filter. There are threads here showing how to make them, but not sure how well they work. If you have the money, then just buy it, rather than screw around. If the smell gets out of control, you can plug the intake and exhaust until you can install a bigger filter etc.
I believe smelling, telling or selling is how you get busted. There are so many awesome strains to pick from on the internet, don't bother with bagseed unless it's from an incredible bag.
Good luck, and enjoy. Seeing your first big bud, is fucking awesome.