for begin
new Unregister[MAX_PLAYERS];one player connect set it like this
SendClientMessage( playerid, COLOR_GREEN, "Your nick is not registered. Register to protect it." );
		SendClientMessage( playerid, COLOR_GREEN, "USAGE: /c register [Password]" );
	 Unregister[playerid] = 1; /// <<< this line
		PlayerInfo[ playerid ][ Logged ] = 2;
		PlayerInfo[ playerid ][ Stats ] = 2;this is in onplayerconnect where player is not register
Unregister[playerid] = 1;this is on onplayerspawn
      if(Unregister[playerid] == 1) {
        SendClientMessage(playerid,0xAA3333AA,"First Register Then Spawn use /c register password");
        SetPlayerHealth( playerid, 0.0 );
}this is in /c register cmd
Unregister[playerid] = 0;
this is help you easily get  registered players
special thanks to me
note if you dont add this
Unregister[playerid] = 0;your are not be able to spawn in game