Buy-In is critical to any endeavor or project. In fact, it's almost as important as the project itself. If you don't have the hearts and minds of your people or clients, it's usually a lost cause. So this is how I do it.

First, break up your group into three categories:

Acolytes - 20% - your staff or clients who will love or sell your product. They love change.
Independents - 60% - those who really don't care one way or another. They wait to see what happens.
Problem Children - 20% - those who will work against or hate your product. They hate change.

This is how you work with each consituency:

Acolytes - They're already bought in, you need to encourage them to be more vocal and motivational about their love. They're the first ones you bring in to whip them up and get them marketing the product internally and externally. Emotion is key here - focus on how to push their emotional triggers.
Independents - Just like a political campaign, these are the people you need to get to win the election. You need to deliver factual information to get them to jump on-board. Show them how it will change the dynamic of their life and how easy it will be to change. Respect their feedback and listen to their concerns - doing this will allow you to grab a larger percentage of this group.
Problem Children - Externally, forget about them (for now) - Internally, you need to read them the riot act. As they hate change, they are also wary of anything new. They tend to look for the negative in certain situations. Patience is a virtue with this group - but at the end of the day, if you are dealing with internal staff, and they don't eventually jump on board, you need to come down hard on them. Get on or get out. You don't need their acerbic attitude poisoning your launch.

Let's use another Apple example with the iPad 2 (you can probably guess I'm an acolyte):

Acolytes - they are planning to wait on line to be the first to own the new version. You can easily count on them.
Independents - will take a wait and see approach. Unless prompted by external influencers (colleagues or kids), they will wait until the item is on sale or there is an overarching reason to purchase one.
Problem Children - PC acolytes who will never give in to any Apple product. They've lived in their domain for 20+ years and will never change. They will use price or flexibility as an excuse not to purchase one. And they will vigorously spurn anyone who picks one up.

Buy-In is a communication process to hold and excite your base, grab the all important middle, and mitigate the outliers.

What do you do when attempting to get buy-in with your staff, sales team, or customers?

Image provided by Amy Loves Yah at Flickr.