To lurk means to join a network, look around, read and watch other people without contributing anything yourself. Not only is this behavior acceptable, it's a good idea before beginning to contribute and interact with others.
But before you can begin to lurk, you will need to sign up for an account, invite a handful of people to connect with you and become your friend. Once you've invited some friends, now you can move around and see how they are using the network. What kind of status updates do they write? How often do you see them interacting with others? Do they post videos, photos, links to other sites?
Observing others is how we learn what is acceptible behavior in any social situation. When you join a new organizaiton, you attend the first meeting and mostly observe. You don't immediately assume you will get on stage and lead the meeting. You watch, see what activities are on the agenda, look to other group members to know when it's okay to chit chat and when it's time to quiet down and begin the meeting.
The same applies to social media. You don't want to sign up for an account and immediately start posting updates about what you ate for breakfast. Once you've watched for a while, you will be able to see that this type of update would usually be considered uninteresting and fails to start a conversation or add to one. When you've lurked for a while, you will know how to post something of more interest that may entice a friend to comment.
Have you found lurking to be helpful as you began using social networks?