Using a job acceptance letter when offered a position shows true professionalism. It is a way of saying “thank you” to the person who hired you, and giving them assurance that they made the right decision. You have presented yourself to them as a professional with your resume, cover letter, reference sheet, salary history, letters of recommendation, follow up note, and any other personal marketing materials you’ve used while job hunting. You went out of your way to make sure that the interview went well, and probably did your homework on the company before going in for that first interview. Now using a job acceptance letter will be a capstone on all your work, and perfect the positive professional image you’ve tried to convey throughout the job search and hiring process.
Do Your Research!
Every time you submit your resume, you should do some research on the company you are applying to. You should look at their web site and see what kind of feeling it gives you about the company. Does it fit in with your values, and what your long-term career goals are? See where they've been and how much growth they have enjoyed over the time they've been in business.
Now that you have determined that this is a reliable, reputable company, go ahead and submit your cover letter and resume.
Be sure and use the company's preferred method of applying, and if they require information from you like salary requirements, include that in your response. Always tailor your cover letter to each job that you are applying for. Don't ever use a canned response. It tells me that the candidate didn't think enough of my company to really look at the job requirements or do any research. And, it tells me that the person is careless and sloppy if they didn't even edit their cover letter. If that's the case, why should I waste my time reading their submission?