Controlling space is one of easiest and most effective ways you have of making your slides easier to read and comprehend.
For instance, the default settings in older versions of PowerPoint created bullet points that all had an equal amount of space between them no matter if they were top-level bullets points or sub-bullets. Indenting and the increasing smaller font size gave some clues as to what was important and what went with what, but the uniform spacing could make it more difficult for the audience to see what the slide was trying to do.
To instantly make slides like this much more readable, simply increase the space between the top-level bullets and tighten up the spacing of the sub-bullets beneath each one so there is a clearly defined relationship that can be understood at first glance. Information that is of primary importance is clearly differentiated and it’s easier to skim over the supporting material in order to quickly get the big picture. (Quick additional hint: If you don’t have enough room to add this sort of additional space, you probably have too much on the slide and are courting death by bullet point.)
To put it simply, elements that belong together conceptually, should be close to each other spatially and elements that are not related conceptually should be distanced from each other.
This technique doesn’t just apply to text spacing. Does the chart or table on your slide have its own title? Is this title closer to the chart or to the slide’s title above it (or is just hanging there somewhere in between?). Positioning the title closer to its chart makes it immediately clear to your audience that they belong together as a unit. Now if the text above the chart is just a bullet point or two, you will want more space between it and the chart so it’s clear they are separate elements.
Remember, space conveys meaning and small changes like these can make a big difference.