How do I mark teeth for a bridge when someone is missing a tooth?

If someone has had a tooth extracted or congenitally missing a tooth, it may be difficult to select the proper teeth for the abutments and pontics. Here’s an example –

The patient is missing #12, but the bridge is from #11-14.

1. Select abutment teeth as: #11 and #14
2. Mark tooth #12 as missing (read tip on how to do this)
3. Select pontic tooth as #13