db:migrate
Using rake's db:migrate is useful for creating/modifying table structures and data and it is quite nice how the way its designed basically give you a paper trail of your development, which I guess is better than hacking the MySQL database or whatever. Sometimes however you run rake db:migrate and it doesn't seem to make any difference. I how found that if you revert back to version 0 this can solve the problem:
prompt>rake db:migrate VERSION=0 prompt>rake db:migrate
Some output about what rake is migrating will be output and hopefully it will migrate all the stuff in your db/migrate/ folder.