What he said.. ^^ additionally, i would skip about 5 lines, draw a line of dashes and on the next line write ' text version of resume pasted below' , skip 5 more lines, and then i would paste a text version of the resume there just incase the company is having trouble with attachments or does not accept them.
Any time you send a resume, be it snailmail or e-mail, you should always include a cover letter. It allows you to present yourself and sho why you are the best candidate. It also provides a way for the headhunter to judge your personality and in the last paragraph, it allows you to make an impression on the headhunter and secure an interview.
You will always be sending the same resume out to companies in your field, but every cover letter should be tailored to the company and job you're applying for.
Check out
this website for a tutorial. Read it all and you should do fine :beer: