make sure you have all the intel. when you do, your buddies will meet you at the ladder
then a little surprise happens. Make sure you have a good amount of health left when you
get to the second ladder

Also don't forget that some tunnels have closed doors. Go upto them and press your use key
to open.

To get out of the Tunnels, go to the marines and let them talk until they stop. Turn to
the secret door and wait until the VCs or NVAs to come out and then shoot them. Then you
enter the tunnel that the VC or NVA came out,then you keep following where it leads and
then will will see a ladder.