Here's my 2 cents.
I read the article that was mentioned, but having installed quite a few headliners I don't agree with all of it. I would wait to install the mirror, visors, etc until the glass is in. Go with the TMI headliner it is the best I have used and very few wrinkles to smooth out. I also use weatherstrip glue (black or yellow) to glue it in with, it doesn't tack up as fast and makes moving the headliner easier. One last trick I have found, do not use windlace to help hold the headliner during install (sometimes it can cut the liner around the pinch welds) I went to the office supply store and bought http://www.officedepot.com/ddSKU.do?level=SK&id=308957&&An=text there are 2 sizes, I use the smaller clips around the front and rear window opening and the larger work great on the sides, I just pull the liner up to the drip rails and hold with the larger clips when stretching the liner.
Hope this helps, Phil
All the above advise is top notch. I did Johnpro's wire trick and also used a ton of the little (3/4" I think) black paper clips. I put one about every 6-7 inches. Good luck, The headliner is a lot easier than it looks. Just take your time, watch the wrinkles and leave the Budweiser til the end!
I'll tell you what I did that worked pretty well. I went to the office supply store and bought a whole bunch of these:
Before I glued anything I stretched and fit the entire headliner using the clips to hold it in place (about 200 of them I think). Once I was happy with the fit I would remove the clips 5 - 6 at a time, glue that area and reinstall the clips moving around the headliner until I was done. I left the clips in place until the guy came to put the front and rear glass in.