Create a welcome message for the new member that has important information like: what you guys do where you are at, contact info, the forum and other tools you use, objectives etc. This is a little work but it help people to feel welcome and grounded in the team. This can be saved and used for any new members.
Take some time to let the new member know how the team works, where you are and where you are going. Please do not do this in general meeting for its ussually very boring and a waste of time for the rest of the team.
Step three: Team Leaders: introduce yourself and other tem members top the new team members.
Make them feel welcome and put yourself in the position of the new member. when you join a time you ussually feel kind of out of place. You know very little on whats going on and how things are done.
Give the new member a well defined task right away that suits his experience and knowledge. The point is make to become part of the team ASAP. and through his contribution that will happen.
Be patient: Be aware that sometimes new members may come in with a lot of energy. This sometimes is owverwhelming. Be patient and remember that these members may become the most valuable members of your team and bring new interesting perspectives.