1st get a good saftey harness system.  Falling is not cool.  Be safe.
Be sure to check out http://www.OSHA.gov & their specific Safety and Health topics on Scaffolding @ http://www.osha.gov/SLTC/scaff.....index.html

The Typical Scaffolding Solutions for Siding and Windows are:

1. Ladders, Ladder Jacks & Scaffolding Walk Boards.
   1. The walk boards can be placed on the inside or the outside of the ladders as they lean against the wall.
   2. Example:
      (above is not a normal setup but gives you an idea what I am talking about)
   3. More Examples: http://images.google.com/image.....k+scaffold
   4. Explanation and Regulations: http://www.osha.gov/SLTC/etool.....rjack.html
      
2. Stack-able Scaffolding
   It's a metal framework that you erect.  It's not typically used by professional siding contractors because they don't plan on being on the wall that long BUT masons use them and it might be a safer feeling solution for a do-it-yourself-er.
   (no offense, I've been there.  35 feet up on bounce scaffolding with no rails is a completely different story once you get up there.)
   
   1. Examples: http://images.google.com/image.....esidential scaffolding
      
      
3. Aluminum Pump Jack System
   1. This probably isn't a great solution for 1 person setups due to the complexity of setup and operation.
   2. Examples: http://images.google.com/image.....+Pump+Jack
      
4. Other Scaffolding Types
   1. There are mechanical lifts and all sorts of stack-able/build-able scaffolding types available.
   2. Examples: http://www.osha.gov/SLTC/etool.....index.html

In Conclusion:

The main thing is to be safe and don't get up on something you don't feel comfortable on.  Remember the Pro.'s do this stuff everyday and it did take them (usually) several months before they truly became comfortable with working off of scaffolding.  Take your time and be safe.