1.Know the expertise of the company you are applying for the job
2.If you have expertise in Java don't apply in a company which works only in PHP as it makes no sense.
3.Just don't post resume to any email id which you get hold of from websites. It may so happen that you mail the wrong person and he may mark that as junk.
4.Please find out appropriate email id's of HR for mailing. They are the persons involved in to recruitment.