The Design section here may help, too.
Regarding curves, etc. It all depends on what you are trying to achieve, as usual. You don't get Bezier curves (you probably do with a plugin but not natively (or at least I haven't found them yet), but I did come across a neat plugin recently for spirals/threadforms: DrawWhorl. It will leave you with a hollow spiral by default, so you have to add in a central cylinder or cone, but it works well enough for me. Like SU itself, it reduces circles to polygons, which is quite good enough for my purposes, but might be annoying if I was driving a 3D printer. It also only really likes UNC/UNF standard sizes (unless you type in the full detail), but that's not a disaster either.
The single thing that transformed my ability to use SU productively was the unbreakable rule that you make a component of the simplest things you draw (every one of 'em!) and the nest them to get complex objects. That way, things don't "glue" themselves to each other unless you tell them to ("intersect with model"). Drawing something and then hiding it for later use (in the right place) also helps me.