How to get post back values?

[eluser]vigna[/eluser]
I am using set_value function for post back values (printing out the post values in the form elements if the validation fails).
The set_value function works fine for the fields where validation rule is specified.
But for those fields without validation rules, the set_value function doesn't work.

What should I do for the other fields to get the post values.

Should I use $this->input->post('field_name') or
store the post value in the flashdata and print it out in the html element

What is the proper method to do this?

Thanks