What do you sell?
I know this is quite subjective. I typically like what I call single-tier items: you take factory items, make them into goods, and sell them. I avoid making chairs, for example, which need hammers and nails first.
Most important to me, however, is a predictable time cycle. I've been using a 3 hour cycle, because I've been making and selling flour bags for a long time. Textiles take 3 hours, and in that time I can make 6 flour bags plus 1 vegetable (I often forget the vegetable). I recently added making sugar, so in 3 hours I can make 6 flour bags and 4 donuts. In the same cycle, I can make 4 cement bags. Overnight, I make flour bags and milk; in the morning I turn some flour bags into bread and sell that.
So basically I sell bread, donuts, cement, and excess flour bags. If I have the time and inclination, I hunt down materials for watches and throw some of them in.
I know this leaves several stores unused or under-used, but I prefer a simpler and more predictable schedule to a super-efficient one.
What do you do?