SKETCHUP:

Key concepts / tools:


Outliner
Nesting
Components / Groups
Layers
Active control display - typing x to multiply or / to divide
Sandbox
Intersect with model
Follow me


If you want to do curvy geometry like this:

you will need register and log in to sketchucation.com


and download and install the following plugins for Sketchup to in this order:


1. 000_AdditionalPluginFolders.rb
2. LibFredo6 4.3c - 31 Jan 12.zip
3. Curviloft 1.2c - 15 Nov 11.zip 
4. BezierSpline 1.4f - 23 Jan 11.zip


For each zip file:


1) Download and Open the archive
2) Select All (Ctrl A)
3) Extract into the Sketchup Plugin Directory

4) Answer YES to overwrite all existing files if any.


Another good plugin is Soap Skin & Bubble:

It can be downloaded here.