If the headliner is like a 68 Camaro and a 70 Nova, It's been a while but here is what I remember.
When taking out the rods Number them front to back, the order is critical. I even marked mine left to right.
Get a bunch ( 50 ) of medium size Butterfly clips from Staple's or Office depot. The one' that are usually black and you squeeze the clip's to open and clamp papers etc. They are VERY cheap and should only cost around $10.
Get 3M spray adhesive.
You will have to trim sides of the headliner down to fit the rods, BE VERY CARE NOT TO TRIM TOO MUCH!
Mark the center of the headliner, so that driver and passenger sides are centered.
Install the headliner on to to rods.
Install the center rod first and then work out from there.
Use the clips to dry fit and stretch headliner into place.
Then you start applying the glue and work from the center to the front or back.
Sail panel area is last.
Here is a link from someone who has more detailed info
http://www.camaros.net/forums/showthread.php?t=46867&highlight=headliner
Ray