The answer to this question is somewhat different depending on the nature of the organization.
For example, if your firm is an old firm with a long history, you will want to do things differently than if it is a new firm. If your firm is old, you will want to ensure that people remember the past for two reasons. You need to give them a sense of belonging to a venerable organization and you need them to know about mistakes that have been made in the past. To do the former, you could be sure that you have pictures of important employees from the past with explanations of what made them important. You could have pictures of important projects your firm worked on. You could have signs commemorating important dates in company history. All of these things would at least give employees some sense of where their firm had been.
If your firm is newer, you cannot do these things. Instead, you will need to try to build tradition. You might try to institute annual events that can become the basis of traditions. You can have trophies made to honor yearly winners and those trophies can be kept in a case in a prominent place. You can have annual company outings of one sort or another and put pictures of those up. In doing these things, you can start to build traditions which will hopefully grow with your firm.