Coleus are considered annuals.* Once they flower and go to seed the parent plant dies.* It's best to keep them in a bright spot for the winter.* They really don't need direct sun.* If you have compact fluorescent light bulbs in your lamps nearby, that should help them along.* Pinch them back so they don't flower.* Over the winter you'll find the lower stems get woody.* You don't say where you live, but sometime between mid February and late March you can take cuttings of the newer growth and root them in perlite.* Once rooted you can pot them up for the new growing season.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.