Ken,
Best advice is take everything in case they have changed their mind about what they want!
You will definitely want:
Application Form EX-16 plus photocopy - available from www. http://extranjeros.mtas.es/ (click on Modelos Solicitudes)
NIE
Passport plus photocopy
Form 790 stamped by a bank as paid (see below)
Your old residencia card IF you had one and it has expired
Padron
Suggest you also take:
2 recent photographs
Escritura or rental contract
Utilities bills
Regarding payment that has to be made in a bank (note not all banks do this transaction but they are listed on the Form) a Form 790 which you cant get from the WWW but they give you one in the Benidorm foreigners office
Good luck
Post us on how it worked out.