One that my wife likes taking advantage of... and which makes the photographers a huge load of money is the following.

Groupon/Living social £20 deals for a photo shoot and a single photo. When you get there you are shown some "upgraded options" you can choose from.

Once the shoot is done you have to book an appointment to come back to choose your free photo (this has to be in person and cannot be online). When you are there they put you in a theatre of sorts, dim the lights and put on some emotional "city of angels" type music, show you a slideshow of photos and then say "which one of these beautiful photos would you like".

Let me tell you. This is a powerful business model that can make a ton of cash if done right.