1. Send a quick, appreciative email.
You appreciate feeling valued and your boss is no different. In fact, studies show that people are more motivated by feeling valued than they are by money. If your boss did something during the day that you can authentically appreciate, take a moment to tell them so. For example, "I really appreciate how you supported me in today's meeting while I was discussing the new strategy for the Jones account. It's so nice to have a boss willing to go to bat for me."
2. Offer a quick progress update on something you know they are particularly worried about without being asked.
Your boss is juggling multiple projects and deadlines. Radio silence about how they are going only creates more stress for them if they have to reach out and ask a bunch of different people about how projects are progressing. So, do yourself (and them) a favor by removing that stress from their plate and proactively informing them of where things stand.
3. Tell them that you are happy to be working there and why.
It only takes a moment to tell your boss that you are feeling happy or fulfilled in your job. Bosses worry about morale, and it will go a long way with them if you communicate specifically what it is that you like about the company or working with them. Again, being authentic is essential. Nobody likes a "brown-noser," so make sure that what you say is genuine and from the heart. Do you enjoy the supportive team-environment? Are you fulfilled by receiving challenging projects that stretch your growth horizons? Then tell them so!
4. Relay any positive feedback you receive from others.
Positive feedback that you receive from others is ultimately a positive reflection on your boss and how he/she manages their team. So, share the glory by passing the kudos on. Your boss has a plethora of "problem emails" in their inbox and they will feel relieved and uplifted when they read about something that is going well. Sometimes, just that little bit of news is enough to turn their bad day around. There will likely be extra bonus points if you can tie the positive feedback you received into something that your boss helped you with. For example, if your boss mentored you on how to help a client cut business expenses and then you received thanks for that, be sure to acknowledge your boss's assistance in developing your skill set.