most important tip i'd give in the coverletter/application process is to do your research and be focused.
i just received an "application" the other day from a student in my area looking for an application, and while it had a portfolio and CV attached, i didnt even get that far as the email just turned me off.
1. "dear sir/madam" intro. these days with the internet its not hard to find a person to address it to. esp. for a small consultancy like my own (i'm the only one there, and my name is listed prominently on the website). if you can't find a name to send it to, at least "dear hiring manager" or something of the like is OK.
2. the application was looking for an "industrial designer position". again, my firm is pretty focused in footwear, so i wouldnt really have such a position. i dont think the applicant even looked at what i do before applying.
3. the letter didnt even mention anything about my firm (company, product area focus, etc.)...why would i even think of hiring someone that doesnt even have a clue what i do?
4. the letter did give a brief bio, but nothing relating to anything that would be useful in my consultancy. ie. human factors, like to play backgammon, etc. again, do your research.
the best approach i believe in coverletters/emails (which as Yo said are almost more important than portfolios (given that nobody will see your portfolio if your intro is not appropriate), is to be specific, focused, and to the point.
a. address it to who you are targeting (ie. HR, studio manager, sr. designer, etc.) and have the letter body focused on language and things this person would respnd to.
b. open with your name and the position you are applying for. if its a posted position, reference where you saw the posting.
c. give a brief bio of where you are currently, and highlight the relevant experience/accomplishments specific to the job you are looking for. if its a design manager position, talk about your management experience. if its a position specific to a product category, or industry, talk about your experience in that field. be to the point, as specific as possible (ie. not just "i designed some X", but "i designed 4 models of X that were successful in the market selling Y units" , etc.)
d. specifically mention some aspects/requirements of the job posting and how you are capable in those regards (ie. if sketching ability is mentioned in the posting, talk about those skills, or CAD, etc.)
e. close with a mention of the attached portfolio (ie. please find attached my portfolio which contains further samples of my Z abilities, projects, etc.) and reiterate your bottom line contribution you feel you can make to the company/position (ie. "I feel I would be able to significantly improve the efficiency and market potential of XX brand working as sr. designer, due to my proficiency in sketching and quick model making given my experience handling many projects at a time").
f. also be sure to clearly note your contact info ("if you have any questions or qould like additional info, you may reach me at
xxx@xxx.com or 555-555-5555
g. best regards, with thanks, etc.
R