Decisions to be made have to be put on a platform (IT-based) in order that everyone can access them and enter his/her knowledge or point of view. Even for big decisions like the acquisition of another company the executives will get a broader picture of all the circumstances, possible issues to consider and problems to be solved.
Steps to be taken
The application is the technological foundation, which makes it possible to give everyone the opportunity to contribute.
Inviting people to contribute and sharing knowledge has to become a part of the culture and corporate DNA.
Start small with one group or one department.
Make every information transparent to everyone in the team.
Invite them to contribute to the decision making process (still decisions will be made by those who are in charge / are responsible and have to bear negative consequences for bad decisions.
A kind of reward / gamification system could help to encourage people to contribute.
Use failures as a chance to learn.
You need a supportive appreciating atmosphere to keep the process going.
In the future there might be chances to share responsibility and thus include more people in the final decision making and not only in preparing decisions.