Adding:
rails g migration AddFIELDNAMEToMODELENAME FIELDNAME:TYPE
For example:
rails g migration AddNameToUser name:string
Removing:
rails g migration RemoveFIELDNAMEFromMODELENAME FIELDNAME:TYPE
Renaming:
rails g migration RenameColumnName
then in db/migrate/xxxxxxxxxxxxxx_rename_column_name.rb, add:
rename_column :table, :old_column, :new_column
And of course:
rake db:migrate