Migration from Ruby 1.8.6 (my current release) RoR 2.0.2 (my current release) to the best of today

Hello, i want to do a Migration from Ruby 1.8.6 (my current release) RoR 2.0.2 (my current release) to the best of today. I want to know if you have any ideas on the steps to do this migration, and which version of Ruby and ROR do you recommend? and why?