I haven't grown it for years, although I'm still a severe addict.
I used to get my seed right from Gurney's Seed, although it doesn't look like they still offer it.
The first time I bought seed, I opened up the package and looked inside without seeing anything. Unfortunately, I held the seed packet a few inches above my palm when I dumped it out and the almost microscopic seed blew away. Much to my surprise, it is almost like dust! I've yet to have seen a seed smaller than tobacco.
Here in North Idaho, I had to start my plants in February and due to the seed size and not being able to really plant them, I'd use a pot and open up the packet and sorta wave it over the soil, hoping that some fell in. Some weeks later, sure enough, there were so many seedlings, I'd have to start transplanting them.
I'd set them out after all danger of frost in June and man, did they ever take off then! By the end of August, they'd be over six feet tall, with big 'ol leaves.
I planted burley, which I always found rather harsh, compared to what I was used to smoking but would mix it with store bought tobaccos to make it more palatable and then gradually try to cut down on the store bought stuff as I got poorer through the winter. Folks around here were surprised that we could even grow tobacco, since it is viewed as a southern crop, so everyone wanted to try it. Didn't have many converts though because of the harshness. The only rave reviews came from cigar smokers, a few of whom got hand-rolled cigars for Christmas each year.