I agree with using Styles as per the previous replies; they can take a bit of time to get used to but are well worth the little effort required.
One styles tip which has worked for me, if you're using styles a lot, is to set the "Default Paragraph Style" to a font/size/colour you rarely use in your work. That way you have a visual reminder that you haven't set the styles properly in frames which are in this unusual font/size/colour. Essentially you can see at a glance that something is wrong.
This is especially useful if your default is visually close to what you really want to use. For instance, if your default is "Arial/12pt/Fixed Line Spacing" and your style is the same but using "Align to Baseline Grid" instead, you might not notice when a frame changes back to the default style until, of course, it's been expensively printed! I've mostly noticed this using "Get Text…" to replace text already in a frame. "Get Text…" doesn't just replace the text but also reverts the text back to the default style (although this might be overridden by a setting I haven't found yet).