Choose the right line
If you can, get behind as many solo adults as possible. Business travellers know what they're doing and will keep the line moving quickly. Families and first-time holidaymakers (such as that honeymooning couple who are only paying attention to each other) are going to slow things way down.
The screening agent wants to see one thing: your boarding pass. So put your ID away and have your pass in your hand as you approach. If it's on your phone, have the screen up and ready to go. And forget about using your smart watches: It's awkward, if not impossible, to fit your wrist under the scanner.
Prep in line
Take your jacket off, along with any cardigans and zip-up/button-up sweaters and drape them over your luggage or arm. If you know you're going to have to take your shoes off, consider undoing the laces in advance (just tuck them in your shoes/boots so you don't trip on them).
Upgrade your gear
Remember that laptops must be taken out of any bags and placed in a separate bin. If you frequently travel with a computer consider getting a bag with an exterior laptop pocket. This makes it easier to take the device out but, even better, makes it a cinch to slide it back in.
If you get selected for secondary screening, you might have to turn on your electronic devices (yes, this still happens). So make sure they're charged before you get to the airport. Failing that, you better hope you didn't check your power cord.