Leading Engineers - Influencing

Animportant leadership skill is influencing and you touched on this in the answer to the question of leading a project. I want to dig a bit deeper into influencing, because i believe this is a very important skill set for senior engineers. How do you go about influencing other team members or teams to use your solution instead of writing their own? It can be really difficult actually, to have influence, because many engineers don't actually like to feel influenced.