When I’m generating a migration, I usually don’t go any deeper than specifying column_name:data_type on the command line, and often I only use the command line to generate the file itself.

I don’t know that the other options really save all that much typing, but stopping to think about the other options for a few seconds might just help avoid having to go back later and add things.

Elementary things I don’t make enough use of:

• rails g migration AddXXXtoYYY automatically creates an add_column for table YYY for every column name specified.
• rails g migration RemoveXXXtoYYY automatically creates a remove_column for table YYY for every column name specified.
• Specifying column_name:data_type:index also adds an index to the new column.
• rails g migration CreateJoinTableXXXYYY will produce a join table.