I think the biggest thing is to not treat an idea like it's particularly precious or important as it is...but rather as something to nurture and watch grow.
It's really easy to get excited about a great concept or a particularly effective lateral hop that opens up a lot of possibilities, but two things seem to keep coming up in my little corner of the world.
1) No matter how complete an idea feels at first, the more context and analysis is added the more it begins to change just based upon the new perspectives added. I think this is a natural part of how our brains work...as we're biologically designed to see the world through the lens of a smaller group, it's impossible to instantly understand how a concept would interact with hundreds, thousands, or millions of people.
2) Ideas are like children. They're going to grow and change, and it's up to you and yours to grow them in the best possible direction rather than cling to your initial view as if it's important for it to remain pristine.
There's always a little bit of an emotional battle there (We get attached to our ideas! They're our little brain babies!) but the payoff for taking the 'let's see how this baby can evolve under our care' approach is pretty tremendous.
Also, as Vivienne Lee said above, get it in front of people (like customers) who are going to poke holes in it, jab at it, and otherwise try to break it. The more different mindsets added to the process the better, and while not every single issue and concern is necessarily relevant...it's always better to have been forced to consider something than it is to be oblivious to it.