I have to add, besides the personal preference of vaping, the eJuice also plays a part on making the right choice. I've had a liquid that didn't like a lot of heat (power, wattage), otherwise I would get a burned flavor, where as another needed lots of heat, in order to actually get the full satisfying flavor.
Due to experience, I use either single, or dual coil(s). However, when utilizing a single coil, it's a simple single wire, a twisted wire, or up to a dual inner core Clapton coil.
In general, building the proper coil(s) does require try and error. Eventually, you'll know what coil(s) you need to build. Of course, it also depends on the atty, you're utilizing. Some attys give you the option of building either a single coil, or a dual coil. Others give you just one option.