CHANGE 07/27/16: 50 Credits. AND The Family Boost is gone, so everything below about it, no longer applies.
CHANGE 09/27/16: 35 Credits. People started buying these now that there is an implied discount. Still the Family Boost is still gone. I personally would love to see it come back.
Probably the one most important thing, is to not have your profile viewable to only Friends, or to require a Salute. People will just move on, but some will friend request you.
I'll start out by saying that this bling is rarely run by itself, but it can. The biggest parts about it, is the abilty to have your profile rated again. Everyone in your family gets an automatic 11 rating, which is most useful for the level 58 requirement for being top ten HOTTEST for the day, as well as hottest guy or gal for the week, and your lifetime fubar rank.
CHANGE: January 2017 - Level 58 Top Ten Hottest is no longer required.
For the most part, you should run this with a Boomerang. Some users start both together but you get more benefits if you time it right. The Boomerang lasts FOUR hours, while the FAMP lasts THREE hours. Try to start the FAMP close to 30 minutes after your boomerang.
My Blog about Getting More Profile Rates explains this with running combinations if Boomerangs, FAMPs and Big Bangs.
Combining this with boosting your family, you can rate 55 people (65 with VIP) if you do it right. The boost can be found in MY - Abilities.
What they don't tell you, is that each boost lasts five minutes longer. SO the best thing to do is have a list of who you want to add, then five minutes before you run the Famplifier, you do the Family Boost Extreme. Open (or refresh their page) and if they are not already in your permanent family, and purple link will appear for you to add to your boost. Five minutes is plenty of time to add 15 people.
Additionally, and I'll explain this in its own blog, you can combine this with both Boomerangs and Big Bangs, and get a few undocumented extras.
When you have a boosted family, you will see the boosted people here.
And when you are in someone Famplifier, the News Feed will show many of the rates you receive through their famps.