Layout & Margins
Keep your margins generous. There's nothing worse than too much information crammed into a small space - long line lengths will hamper readability. It is best to have ample space on all sides, with the bottom margin generally being the largest.
If in doubt, keep the default. In most situations, you'll want to preserve the default margin settings. In most applications the default margin settings will be optimal for the paper size you specify.
Consider columns for presentation. Certain sections of your CV, such as your work or education history, will benefit from a columnar layout. Doing so can provide a more logical, yet compact approach. Avoid splitting long paragraphs over columns - keep columns for summarised information, and stick to paragraphs for longer text.
Keep spacing between elements - particularly between sections where you've used a different layout (i.e. the transition from columns to paragraphed text). Whitespace helps keep the distinction between different sections, and is particular important if you're varying the layout style.
The tools you use will reflect in the final output and format of your CV. Much will depend on which tools you have available, but it's good to be aware of the alternatives.Microsoft Word
Your CV cannot comprise of two sides plain, unadorned text - you need to break a potential essay into easily digestible chunks. Careful use of headings, breaks and other tricks can help break up a wall of text into a beautiful hierarchy of naturally presented information.
A larger type size is the perfect way to draw the reader's eye to headings - and coupled with a judicious amount of spacing will serve to break the document in a pleasing fashion. It's best not to use too large a font, however - just a few points more will suffice. If your body text is 8 or 10pt, your headings should be somewhere about 16pt in size - no more than double the size of your body text.
Underlines and outlines can also help - if used judiciously. I'd probably recommend against using text underlines in most circumstances (italics is best for emphasis), but a page rule (a line across the page) can make for an effective page break, particularly for a major section break or following columnar or tabular data.
Bold and italic are also two very important tools in your emphatic arsenal - headings should be bold where suitable, and certain passages in text can be highlighted in bold. Italics serve less as a highlight and more as a softer emphasis - for instance, in cases where a certain differentiation from the body text is required but not to the degree that bold would provide.
Avoid colour emphasis. For many of the reasons that I mentioned in the last post regarding the usage of colour - notably reproduction difficulty - but also for issues of readability and a lack of convention - colour has never historically been a source of emphasis in text, and today colour tends to be used for interactive elements (i.e. hyperlinks in web documents) rather than to provide an accent.
As with so many aspects of CV design, the trick is to be conservative - black and white trumps colour, simpler layouts and more compact structure are best, and classical typefaces are the ones to stick to. There's really no reason to attempt anything too avant-garde, when the basics are really all you need - get the basics right and you'll stand out more than you might otherwise suspect.