Consistent use of fractions
Probably most people are familiar with the autofill character fractions* for the most commonly used fractions: ½, ¼, ¾; so those character fractions are predominantly used instead of the character combination fractions** of, for example, a 1, a slash, and a 2. Character fractions are fine to use unless you're going to be using other fractions that do not have character fractions – then you have something that looks like this: ½ to 5/8. Not really that appealing or professional looking.
If you are using PowerPoint 2007 and above, you have access to characters that will make the character combination fractions that look like character fractions.
The screenshot below explains a lot. Take a look at what is available to you and become familiar with how to create consistent looking fractions in your presentations.
All you need to do is be in text mode, bring up the symbol library (Alt-i, s), find your character, click on it, and click on insert. To return to your text, click Cancel. To insert sequences of characters, just click on the character (the numerator) and click insert, find the next character (a slash), and then the next character (the denominator).
If you're using PowerPoint 2003, it's a little less push-button. You can, however, create fractions that are reasonably close to character fractions by applying superscript and subscript formatting to the numerators and denominators. Getting the sizing right is a little bit of a hit-and-miss process. Try a few sizes until you get a similar representation of the fraction. If there are too many of these fractions to deal with in PowerPoint 2003, it might be a good idea to just use combination character fractions throughout the document. The idea is to make your presentation look consistent and professional, but productivity is always a factor in deadline situations. Use your best judgment on this one. Just try not to mix character and character combination fractions.
* Character fractions are fractions that are only one keystroke or character; they look like this: ½
** Character combination fractions are several characters that together make a fraction; they look like this: 1/2