Another lesson from The Action Hero's Handbook, which this time is also pretty useful for your everyday nosey neighbor, jealous ex-lover, private eye or other such non-heroic profession. Let's get started!
1. Determine the topic of conversation beforehand.
Kind of a no-brainer, yeah, but it'll certainly help to know whether you're spying on drug dealers, contract killers or suburban moms gone wrong. In any case, knowing the topic will help limit the vocabulary used.
2. Position yourself in front of or to the side of the speaker
If you're better at tongue-reading, position yourself slightly to the side. If lips are your specialty, you'll want a frontal view.
3. Stay mobile
You may need to reposition yourself during the conversation as the speakers move their heads from side to side and shift their bodies. But be smart -- a Segway is great for mobility, but not so great as far as the whole "incognito" thing goes.
4. Read consonant sounds using the following basic criteria
"¢ P, B and M are formed with both lips together.
"¢ F and V are formed with the top teeth on the bottom lip.
"¢ Sh, Ch, J, Y and Zh are formed with the lips in a large pucker.
"¢ Th sends the tip of the tongue sticking out through the teeth.
"¢ S (C) and Z (X) are formed by the lips making a smile.
"¢ R is formed by the lips making a small pucker.
"¢ W is formed by the lips making a closed pucker.
"¢ K (hard C, Q), G (hard) and H are formed with an open (neutral) mouth and are never perceptible. Experience and context will help you discern them.
"¢ T, D, N and L are formed with the tip of the tongue moving up to the top of the mouth and then down (seldom perceptible -- again, context and practice help).
5. Multiply your exposures
Use a team of readers in multiple locations to get the whole story. Station the readers in various proximities to the speaker(s). Each reader will obtain a different part of the conversation. And if you fail, at least the speakers will feel weird, wondering why a roomful of people are all staring at them.
Of course, this is just the beginning. Eavesdropping is a learn-by-doing kind of activity, so get out there and start minding other people's business!