Use actual copy early in the process
Balsamiq recommends[1] using the actual copy that will appear in the final design early in the design process for two reasons. First, it lets you see how real content will fit the layout. Second, relevant wireframe text encourages more thoughtful feedback during wireframe review sessions. If the copy isn't ready yet, it's better to quickly draft text similar to length and tone of voice so people can give their opinions on what it conveys.