Listen, learn and communicate.
The battle for communication is a fight fought on two fronts. As a designer you wish to see the success of the business you put the majority of your time into, but at the same time want to see your clients put similar effort into the understanding of what design can do fortheir business. This means that both sides must open up to listening, learning and communicating.
Client participation is crucial, nobody understands their business as well as they do. That's why you should be asking alot of questions — to understand clients real needs. And you should expect your client to do the same.
If you are working for a client or a company that is not clear about its goals (or is actually hiding them), you are fucked, you should leave immediately. You will never be successful there.
What does it mean?
Design what is true. Create useful, straightforward and simple design — you should never confuse users with an abstraction, instead provide a solution for their problem. Good design doesn't mislead, it helps the user — it's honest and true.
A button is a button.
Often designers find excuses to try and impress users / clients with "Creativity". "Creative" design makes things non–functional and almost impossible to use. That does not mean you can't make something aesthetic; but it is more important to know that design should be useful and functional — not just something you keep in your hoarding stash.