I am trying to select all input fields on a form (except buttons and checkboxes).
I have got as far as to select all the form input elements on a form with id \"myfo
$("#myform :input:not(:checkbox):not(:button)");
You can use :not() combined to :checkbox and :button selectors:
$("#myform :input:not(:button):not(:checkbox)");
and test it with success with the example provided in the documentation of :input
EDIT: :input also selects textarea, select, button and input[type="hidden"] according to documentation (and a useful example)