You will want to write extensions.
You will need to learn basic Ruby first.
Then learn the SketchUp API that enhances Ruby.
---> Ruby Learning Resources [WikiLists] - #10 by LE_GALL
Search this category for “example” or “code”. (Use the 
search icon top right.)
I also linked the Trimble tutorial examples above.
There are also examples you can download from the Extension Warehouse …
- Example Ruby Scripts <— Withdrawn Replaced by the tutorials examples
- Shapes
- Utilites Tools
- Window Maker