how to delete junk email from your gmail inbox

For social networking, we have got several emails from them. most of them are totally useless . so you can delete all of them in  a single click.  for this type:  in:inbox     -in your search box, select all or define the selection and delete all.

in:inbox before:2009/12/31   :  search it for for deleting those mail before that date...all show up and select all to delete.

thank you.