Principles
DRY - Don’t Repeat yourself.
http://www.jensjaeger.com/2008/04/das-dry-prinzip/ (german)
http://en.wikipedia.org/wiki/DRY
KISS - Keep it Simple Stupid
http://www.jensjaeger.com/2008/04/das-kiss-prinzip/ (german)
http://en.wikipedia.org/wiki/KISS_principle
General
General Ruby Styleguide
http://rubygarden.org/ruby/page/show/RubyStyleGuide
General Rails Styleguide:
http://wiki.rubyonrails.org/rails/pages/CodingStandards
Language
Everything in the source code must be written in english. Including comments, variable names and function names.
Encoding
All files must be encoded with UTF-8.
Methods
Every method should have a meaningful name.
For a procedure name use a strong verb.
Example:
Report.print
For a function name use a description of the return value
Example:
Report.publishing_date
Avoid meaningless or wishy-washy verbs.
Descripe everything the method does.
Make names of routines as long as necessary.
The average length of methods should be from 15 to 20 characters.
Variables
Every variable should have a meaningful name.
The most consideration in naming is that the name fully and accurately descripe the entity the variable represents.
The average length of a variable should be from 8 to 15 characters.
Use shorter name only for iterators in really short scopes.
Example:
reports.each do |r|
r.print
end
The scope of a variable should be as short as possible.
Arrays should have a plural name.
Example:
reports = Report.find(:all)
Everything else should have a singular name.
Example:
report = Report.find_by_id(1)
Constants
Naming like variables.
There should be no numbers in the sourcecode. Every number should be a constant defined in environment.rb.
Example:
PAG_PAGES = 10 #items per page for pagination
Comments
Comment as much as possible.
You shouldn’t comment WHAT your code does (this would be hurt the DRY-Principle), you should comment WHY your code does something.
Stay DRY
If you are doing something more than once, extract it into a method. This is especially the case when it comes to conditional queries. So instead of writing:
@reports = Report.find(:all, :conditions => ["deleted = ", 1])
you should write a method:
class Report < AR::B
def find_deleted
find(:all, :conditions => ["deleted = ", 1])
end
end
Paranthesis
Use paranthesis with “standard” method calls and no paranthesis for helper-style hash arguments. Example:
Report.find_by_id(1)
#instead of
Report.find_by_id 1
but
link_to "view", { :action => "view" }
#instead of
link_to("view", { :action => "view" })
Acknowledgments
Thanks to Florian Gilcher for the helpful comments.
. Im 
werden zahlreiche praktische Beispiele für User Centered Design beschrieben.
von Benjamin Lee Whorf.
das Vorgehen anhand von Beispielen beschrieben und nennt ausführliche Test Patterns.
dieses in aller Ausführlichkeit beschrieben. Fowler listet