You can use FullProf, Maud or similar programs to find the lattice parameters. Many materials behave metallic, semiconductor or insulator. Fitting an XRD pattern does not depend on procedure as you mention. But physical properties that your sample presents may have. The term "lattice" means you have  a long range order, which is a crystal. And yes you can calculate their lattice parameters.

http://www.doitpoms.ac.uk/tlplib/xray-diffraction/peak.php

go to the link you will get your answer......

TOPAS software is also helpful to to get the ans of your query. By the way, XRD spectra is not right terminology you must use XRD pattern

I think you mean X-ray diffraction patterns and not spectra. The fundamental physics are different. I agree that the TOPAS software or FullProf are good. You can also read some fundamental textbooks in crystallography on how to do it.

Thank you very much to all of you for kind response...