With the advent of word processing, desktop publishing and laser printers, there is no excuse for a non-professional presentation. Right hand justify the text for a cleaner appearance. Ivory, light blue and light gray are distinctive and attractive, yet conservative. Use matching stationery and envelopes for your cover letters. Proofread and double proofread.
Errors are unacceptable.
Leave lots of white space. Readability is as important as content. Stay away from long paragraphs of more than 6-7 sentences. The one versus two page dilemma is a constant point of concern. Years ago, the Resume God said Let your resume be one page.