What I think might make this a little unclear is that your question seems to be something that you could answer by doing a Google search on some persuasive communication techniques. I didn't close the post, but I suspect that the people who did vote to close may believe there's more to the question than what you've given us, and to them, that may mean it's a bit unclear. No one likes to answer a question only to have the asker say, "No! I already thought about trying X, but that won't work because my problem consists of Y."
Let's assume you already did some research on communication techniques and discovered some helpful information but are just unsure of how to apply those techniques. If you can edit your post to describe why it is your stuck, it will make it more clear to the answerers exactly what it is that you don't understand but on a much deeper level.
Not only will this likely get you a really great answer, but it will also be more helpful for others who have a similar issue that wasn't solved by simply reading some guidelines on good persuasive communication.
I think the question is now too broad.
It is going to be very hard to answer this question because effective varies greatly depending on what you are trying to suggest, and persuasive is going to vary based on who you are trying to convince.
I am not going to cast a reopen vote to a question that still needs to be closed.