SPServices AddUserToGroup RemoveUserFromGroup

Lately there are some questions about the AddUserToGroup and RemoveUserFromGroup functions of the SPServices library.
Here some examples:

$().SPServices({
            operation: "AddUserToGroup",
            groupName: "<groupname>",
            userName: "<displayname of the user>",
            userLoginName: "<domain>\\<loginname>",
            userEmail: "<emailaddress of the user>",
            userNotes: "<note to add>"
        });

Replace <groupname>, <displayname of the user>, <domain>, <loginname>, <emailaddress of the user> and <note to add> with yours, without the < and >.

$().SPServices({
            operation: "RemoveUserFromGroup",
            groupName: "<groupname>",
            userLoginName: "<domain>\\<loginname>"
        });

Replace <groupname>, <domain> and <loginname> with yours, without the < and >.