This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
I am hoping that you are using struts2 and action class implementing the ModelDriven interface.
Pass all the field values while you are calling the action through links. Also make sure the parameter names in the link must match with field/variable names defined in the Bean/action variables. Thing is framework must be able to make Bean by using the parameters you are passing.
I think framework will take care of whether you are calling using Post or Get.