Peter Connolly does a good reconstruction of basic crucifixion in his book "The Holy Land". He has illustrations of the remains of a man who was crucified in Romans times, including nails still in place in the ankles. I've also read 2 or 3 medical articles about the presumed physical effects, a while back.
I would not assume there was much of a "standard procedure" regarding flogging, stripping, gender, etc. It all depended on the victim and the circumstances. Certainly women were crucified at times--during the siege of Jerusalem in c. 70 AD, the Romans were tacking up anyone they caught trying to escape the city. Up to THREE HUNDRED people per day! That got old, fast, so the soldiers experimented with new and different poses, just for fun.
Anyway, from what we know, it does seem that nailing was typical, and there wasn't much reason for tying. Connolly shows evidence for the nails to be driven through a block of wood first, to serve as a "washer" (so the nail head doesn't just pull through the limb), and this would also serve to keep blood from spraying on the guy with the hammer. Remember, crucifixion was specifically meant to be the most painful and horrible way to die! Ropes are for wimps.
Also, there was no need to have the victim way up in the air, forcing the executioners either to haul the guy and the crossbar up the pole, with all manner of ropes and ladders and such, or (worse) nail him to a cross lying flat and then laboriously hauling *that* upright. That's a huge amount of work.
Much easier to have the cross set up first, in nice solid holes or sockets, with the crossbar at about eye level. A couple burly soldiers hold the victim against the upright and extend one arm to the crossbar--I suppose a quick lashing of rope might help for that, or just a couple gut-punches. Stick the first nail anywhere along the forearm between radius and ulna and hammer it in. The victim will likely be a little more compliant at this point, as you grab the other arm and repeat. Now just lift his feet and drive one nail through both heels into the side of the upright. Done! No heavy hauling or cleverness required. Remember, soldiers stuck on crucifixion duty are the guys who flunked out of latrine duty, so they are neither bright nor energetic. Keep it simple.
No "seat" or anything is needed, in fact it's kind of counterproductive. If the feet were lifted up under the victim's butt, he can kind of rest on them. But that may pull on the arms, which not only hurts them (a lot), but puts pressure on the lungs. It's hard to get a full breath, and there's a feeling of slow suffocation. So the victim pushes up with the legs to get a breath and relieve the arms, but that hurts the nailed ankles. So he relaxes his legs, the arms hurt and he can't breath, so he pushes up. On and on, keeping the wounds bleeding.
The medical articles I read all came to different conclusions about the exact cause of death, whether it was blood loss or shock or whatever. But really, it's everything! And it can go on for hours or days. And the clever bit is that the victim is torturing *himself* to death at this point.
If you can't wait around that long, break the legs. That brings up images of big clubs or mallets, but really all you need to do is push on the knees, and the lower legs will break agains the upright beam. Possibly the femer, too, but no need for that. Once the legs are broken, they won't support any weight, and the victim will basically suffocate, if shock and blood loss don't get him first.
The exact shape of the cross doesn't matter a whole lot. It's probably safe to assume that the usual shape was either T-shaped or a classic cross simply because of the word "crucifixion". An X-shape, with arms and legs spread, should work fine. And remember that not only was this meant for maximum pain and humiliation (so presumably the victim was stripped first), but the soldiers on duty got to keep any usable clothing or posessions. No point in messing any of that up first, eh?
OH---One more fascinating detail that is usually badly misinterpreted. In the Bible, Jesus is given a drink of something, often translated as "wine mixed with vinegar", etc. It's supposedly part of the torment. Well, that's just posca! The typical cheap wine or wine-vinegar mix that soldiers (and many civilians) drank all the time. So someone had his canteen there. And the sponge on a stick is generally shown as a long pole meant to reach way up on the telephone-pole like cross, which of course we know is unnecessary. And sponges don't grow on the hills around Jerusalem, so what's up? Well, a sponge on a stick was a common implement in the days before toilet paper! Presumably one of the soldiers had one in his pack. And while it's easy enough to give a crucified man a drink from any cup or messpan, it sounds to me like the soldiers were yucking it up--"Hey, don't dirty my messpan on that guy's lips--my sponge needs a rinse!" What a bunch of kidders, eh?
Anyway, I hope that brightens your day! Careful with those nailguns, kids.
Matthew