How do I add myself to the "wheel" group to use cvs?

I am on a Mac (Snow Leopard) and I would like to add myself to the "wheel" group? How do I do that? I there a way I can see all the groups am I in?

You can see what groups you are in using the id command:

$ id testacc 
uid=1089(testacc) gid=1096(testacc) groups=1096(testacc)

the dscl utility can be used to add users to groups:

$ dscl . append /Groups/admin GroupMembership username

where username is the user short name of the user you wish to add to the particular group.

There is arguably a better command to check what group one belongs to. The "groups" command. Example:

$ groups

staff _developer _lpoperator _lpadmin _appserveradm admin _appserverusr localaccounts everyone com.apple.access_ssh com.apple.access_screensharing

The command to add group wheel:

$ sudo dscl . append /Groups/wheel GroupMembership username

Where "username" is your username. Then re-run "groups" to see that you have indeed been added to group wheel, like so:

$ groups                                                  
staff _developer _lpoperator _lpadmin _appserveradm admin _appserverusr localaccounts everyone wheel com.apple.access_ssh com.apple.access_screensharing