Nested Families: We've had window families that were getting to be upwards of 2 MBs making the project file huge (over 140MB). On average window and door families should be 140kb - 400kb (we do have a few ornate doors that are larger) . It turns out one of our users was loading window families into window families into window families. Make sure you purge unused when you're done with your family.
Levels: You shouldn't have to add a lot of levels when they are only inches apart. Too many levels clutter elevations and sections so keep an eye on how your users utilize levels. Make sure your users know that they can OFFSET heights of objects. Levels can be difficult to modify later once they've been established.
Paint Tool: The Paint tool (PT) is for applying materials and patterns to a model surface. You can not import a dwg file (or draw a boundary using detail lines) and expect the paint tool to fill the area within the drawn boundary. The Paint tool is not like photoshop's Paint Bucket Tool.
Sitework - Roads: When I was learning how to build sitework I was using the Split Surface tool to create roads and walkways. It didn't occur to me at the time to create subregions instead. Use subregions to distinguish asphalt roads and walkways from topography. Creating roads and walkways with the split surface tool is a bad idea. Once you split a surface, editing the boundary of that split surface becomes very difficult and often results in "can not triangulate surface" error messages.