Rails Development Tips part-2

• Use database indexes to speed up queries. Rails only indexes primary keys, so you’ll have to find the spots that need more attention.
• Profile your code. The ruby-prof gem and plugin helped me make an application three times faster with only minimal changes to the code.
• Minimize graphic-related dependencies. If your application only needs to make a few thumbnails, don’t waste memory by importing large graphics libraries. Look at mini-magick or image_science for lightweight thumbnailing.
• Avoid excessive repeated rendering of small partials.
• Use CSS instead of inline tags to apply selective styling.
• Don’t use ActiveRecord’s serialize option to store large objects in database fields.
• Use attr_protected :fieldname in models to keep database fields from being manipulated from forms (or from any calls to Model.update_attributes(params[:model])).
• Use Ruby classes and inheritance to refactor repeated controller code.
• Use unobtrusive Javascripting techniques to separate behavior from markup.
• Package self-sufficient classes and modules as plugins or RubyGems.
• Cache frequently accessed data and rendered content where possible.
• Write custom Test::Unit assertions or rSpec matchers to help with debugging test suite errors.
• Rotate the Rails and Mongrel logfiles using the logrotate daemon on Linux.
• Build a reliable backup system.
• Automate deployment and maintenance with Capistrano or Vlad.
• Keep method bodies short. If a method is more than 10 lines long, it’s time to break it down and refactor.
• Run flog to determine overly complex methods and clases.
• Don’t use too many conditionals. Take advantage of case statements and Ruby objects to filter instead of multiply-nested if statements.
• Don’t be too clever. Ruby has great metaprogramming features, but they are easy to overuse (such as eval and method_missing).
• Become familiar with the most popular plugins. Instead of re-implementing the wheel, save yourself some time by using well tested, popular plugins

source :http://nubyonrails.com/articles/massive-list-of-rails-development-tips