Why do you want to convert it to Struts 2? Do you have an actual *reason* for wanting to do so? Does it makes sense to do so from a time or business perspective? Bear in mind that if you've used Struts 1 form tags (or other S1 tags) you'll have to convert all the JSPs. You *could* use the Struts 1 plugin, but IMO it's not worth it, because you're still left with the untestable mess S1 brought to the table.
Other than that, action by action,
JSP by JSP. There is no magic.