Here's what I found. Haven't had much luck with it myself, but this advise sounds good:
A perennial variety which usually performs as an annual. Native to Europe, it has escaped cultivation and adapted to all regions of the United States. The brilliant little flowers have fringed petals of red, pink, purple or violet. An ideal spring flower often blooming 60 to 90 days after planting under ideal environmental conditions. Prefers moist, well-drained soil in full sun. In areas having extremely hot summers, plant in partial shade for best results.

Dianthus barbatus is usually regarded as a biennial, however, it seems to live on for 3-4 years in my experience. The best showing is usually the 2 or 3rd year though, then it declines. I've seen the old fashioned seed strains reseed prolifically and produce all sorts of variations.
Culture wise, OKC1 hit it.

Have a clump beginning to bloom that I forgot was there so must have sown the seed last year. I have sown more seed in hope of more surprises. EP

I have plants I bought and put in the new bed at the edge of my front yard - the only spot that gets some sun for most of the day. Hoping for the best there. When I have grown it before it was on the east side of the house and got sun most of the day.

I've grown it in full & partial sun both. It seems to do better in partial sun for me.
I plant some every year so as some plants are dying, the new ones are ready to take over the spot.

I bought these on Saturday and am still wondering where to put them. I tend to travel a lot in summer and so my plants need to survive without me. Wondering if too much shade would kill it, or if too much sun would fry them! Will let you all know what happens. Thanks for the info.

I grow Sweet William every year in my 'Winter Sown' containers, usually the 10 cent seed packages. They are biennials for me. I LOVE them. They are my favorites of all the dianthus type plants I've grown. I grow them in full sun. They are blooming now and are so pretty! :-)

Supposedly Sweet William grows wild in my Arkansas area. Does anyone have some seed to spare? Thanks

I've had Sweet William for about three years now in a pretty shaded area - does wonderfully there for me. It seems to reseed quite well for me - it's a small corner garden that I filled with seeds from one of those shade gardens in a can. For the most part, the Sweet William, Violets, Echinacea, and Shasta daisies survived out of that seed collection. It's pretty much filled with Sweet William though. Give it a try - they are really, really lovely and smell wonderful when in bloom. Mine last a long time, too!

MsBeckie,
You can usually get a large package of Sweet William at Dollar General for a quarter -- cheaper than paying postage for it. :)