Your staff needs to constantly be reminded of why they do what they do and the process of communicating that to them is very similar to how you communicate externally. The problem is that many organizations don't have an internal advertising strategy. Their internal advertising opportunities look a lot like a blank billboard.
The people you get to work with on a day-to-day basis should be brand advocates. They should be excited about why they come to work because that excitement will drive better performance for you, and even more importantly, for your customer.
So, just as you would in an external advertising strategy, you need to:
Listen to your audience
Talk to them. You need to survey them. You need to understand them.
Act on what they tell you
If you've hired well, these are people who know their stuff and can bring value to your decision-making. But let me say this up-front. Don't ask them anything if you're not willing to do anything to respond to their needs. That's worse than not saying anything at all. At least if you keep quiet, you'll have a slow decline in team morale rather than an abrupt one.
Communicate to them!
Your job as a leader is to rally them. To remind them of why they do what they do because it's VERY easy to get caught up in just 'doing' a job. So after you listen to them and plan out your responses, you need to tell them about it. That's where you get to advertise to them. Remind them of why you do what you do just like you do to your customer in your sales pitch. Tell your staff about the big wins on your portfolio, just like you tell your sales leads. Reinforce your experience and processes internally in similar ways as you talk about them externally.
This will create brand advocacy.
And one of the really great side benefits to having an internal advertising strategy is that as you advertise to your team, you can then do a compare/contrast with the messages you're sending to your customers and other external audiences. That process can yield some extremely valuable results; highlighting areas of inconsistency and helping you improve your advertising as a whole, and perhaps even influencing operational decisions.
Most often, business is a team sport. Be a team leader and communicate!