A straight length, not coiled around a Christmas tree or tangled in a mess. The kind you might put along the edge of a house roof, or along a mantle or bannister.

Also, any ideas for material settings that would make them look like they are lighted? Or is that best done in postwork?

If it's a distance shot, you could just use a texture. To make something look lighted, use the Ambient Color and Ambient Value nodes. That will make the lights look like they are shining, but it won't cast light onto the other objects in the scene. To do that, you would have to create a point light for each lighted bulb, which would be a TON of lights, and would seriously slow the rendering and shodow mapping.

The Yuletide Treasures Tree, sold at DAZ, has posable light strands. For your purposes, you wouldn't even need to pose them, since they start out in an untangled straight line. Don't you wish the real things worked the same way?

The package includes MAT poses to quickly set up the ambient materials for the bulbs.

To do that, you would have to create a point light for each lighted bulb ....

In P6, you can simply use a gather node on nearby materials. In dim lighting conditions, it'll pick up the colours from the brighter ambient bulbs, creating the illusion that they're radiating light.

It's easily done in post, though. Hide everything in the scene, except for the bulbs. Render against a dark background. Take the image into your paint program and apply a gaussian blur, playing around with levels and contrast, if necessary. Then paste as a new layer on top of your normal render, using dodge or screen as the blend mode.

I haven't tried them yet, so I can't vouch for them but EvilInnocence has two light sets here in the Holiday Giveaway.

I can vouch for the lights in the Yuletide Treasure Tree set. They can be loads of fun as they are EasyPosed and you get great looking tangled up knots as well as nice spirals and stuff. Very fun to play with and the tree is wonderful!

Thanks for the tips! I thought those EvilInnocence light sets in the Christmas giveaway were textures for her petals product in the MP, but they are complete props. Including a single light, which could be probably be used for what I need.

Am also considering the Yuletide Treasure Tree. I don't really need a tree, but I might buy it for the lights and garlands. Hey, I've got a lot of vouchers. ;-)