Leading is the distance between the baselines (the line upon which letters “sit”) of successive lines of type. Most presentation programs use a default leading value of 1.0 or 0 depending on your software application. This is ideal for paragraph writing, but not for presentations. The default leading value creates lines of text that are too close together and difficult to read. A better value would be 5 to 15 (or 1.2 to 1.5 depending on how your presentation software calculates leading). This makes projected lyrics easier to read because there is more space between successive lines of text.
If you do decide to use a larger leading value, be careful it does not add too much space between your lines of text. Too much leading makes lines of text look isolated from one another and therefore, more difficult to read.
To learn more worship lyric projection best practices read The Worship Media Handbook.