If back up slides are needed to provide additional detail, you want to follow the same protocol as you used with your primary slides — glance & grab. Assuming that any back-up slides contain information relevant to what you are talking about, make sure the slides are also:
- Subordinate to you as the speaker (remember, you are the headline act)
- Visible to the entire audience (don’t find yourself apologizing to people in the back of the room)
- Pictorial (whenever possible, use an image to carry the essence of the message)
Thank you V.R. (apparel industry) Cypress, CA for your question!