Along with consistently praising praiseworthy acts (empty praise is a morale killer) a good manager must also consistently and fairly deal with disciplinary problems. A manager unable or unwilling to confront poor performance will engender poor morale -- if you see other employees "getting away" with poor performance, etc... you will not be as motivated to do your best. If a slacker is praised at the same time as you are (e.g. boy your team did great -- when it is clear to everyone that only one person was responsible) then everyone will suffer a collapse of morale. If disciplinary actions are seen as inconsistent or unfair there will also be many problems.
I agree that it is more about general, daily treatment than activities. Some businesses will try to have 'get to know you' activities for new employees. This can help to create a sense of belonging and a team atmosphere. Other businesses will have group activities like a company dinner or picnic. These types of activities do improve moral because it allows employees to get to know one another. They feel more cared for and more connected to the company. They are more willing to work with their fellow employees when they know them a little better.
I too agree with post #2. Rewarding employees for hard work will increase the moral of workers. At the same time, people tend to like to be appreciated. Therefore, even if a person only tells another person they are doing a good job, morale will be high.
I agree with Post #2. I would also like to add that good leaders naturally inspire good followers. To be treated fairly, justly, and kindly will go farther in building morale than treats, rewards, or incentives will. To know that my boss values my opinions, highly esteems me as an individual, and cares about my welfare is all I would need to keep my morale high!
I think that activities are probably less important to morale than the general way in which the manager treats workers on a daily basis. A manager can try things like contests and company functions and other things that are meant to be fun, but morale will only be good if he or she treats workers well every day.