Originally published as a note on my Facebook page Nov 17, 2010.
1. Use explosive sniffing dogs and/or electronic explosive sniffers (not scanners). Note that these are effective at a distance and do not require any invasion of someone's privacy.
2. Use metal detectors to detect guns, knives, etc just as they've been doing for 30 years.
3. Increase the security of cargo and baggage (including carry-on), use improved scanners, sniffers, etc. There are no major privacy or health concerns involved here, and a bomb in the baggage/cargo area is absolutely the least desirable location. There is always a weakest point in any security system. Criminals will usually attack the weakest point. You want the weakest point in airline security to be with the passengers. If the threat is in the passenger compartment, the passengers, crew, and air marshals have a chance to stop it, as they have done repeatedly since 9/11. If it's in the cargo/baggage compartment, you're dead.
4. Allow behavioral profiling. Said in a less politically charged way, allow the screeners to perform additional screening of someone whom they believe looks or acts "suspicious" (e.g. they have probable cause to investigate and if needed perform additional searches). There will need to be limits, so that it's not abused. After the first 2 screening steps, this should rarely occur, but it's important that it be allowable.
5. Recognize and acknowledge that no amount of security is going to stop all committed terrorists. There is a point of diminishing returns where the "unreasonableness" of the security exceeds any theoretical increase in safety. Therefore, there is such a thing as "good enough" security, and the final security is ALWAYS going fall to the air marshals, passengers, and crew of the aircraft. Everyone except the TSA has realized this fact since United 93. Invading someone's privacy adds no more security.
Minor edits to the above.
While the above is my own model, it's come to my attention that this is a slightly simplified version of what Israel uses at Ben Gurion airport, an airport known for effective and efficient security that is not invasive. For more info on the Israeli airport security, see:
Bruce Schneier's blog on TSA issues.
A similar proposal on cnn.com