The plasma places in Gainsville FL work like this:

Your first visit usually takes between 2-3 hours because they almost do a complete physical on you. They need to know all of your vitals, and complete family history. If you pass and are eligible to donate than you go through a process that you will go through everytime you donate.
Everytime you will have to give your weight, temp, and blood pressure. If your pressure is too high or low that particular day they won't let you donate. If you loose too much weight within the week you can't dontate.
Usually they have a big room with abunch of beds with a plasma machine connected to each station. They put the IV in your arm, and what the machine does is takes out blood, spins it really fast to seperate the plasma, then puts the blood back in. They don't do it all at once. They do it usually in 15 minute fragments. You usually have a jug that you have to fill up. It's based on weight. The more you weigh, the more you have to donate before getting paid.

The ones in Gainsville offer you up to 120 per week, and that is going twice, at least two days apart. They will also stamp your hand for a black light to make sure you don't jump from one center to another. Which people do that anyway. Just wash your hands!

They also do specials where you can recruit people for bonus money, and on or around holidays they'll do drawings and bonuses for people who actually still come in. Also like every 5th time you get a bonus.

The trick for donating is to bring a squish ball or something to pump your hand with when it's getting blood out. It will make it go by quicker. The average person takes between 45 minutes to an hour to fill their jug up.
Also to make the time disapear they usually have tvs playing movies and a wide variaty of magazines. You can bring your own reading material and you can also bring a blanket because you WILL get cold as a witches tit when they put the blood back in. And they have to keep it like freezing cold like a hospital so germs don't spread.

Oh yeah, don't know if its just in Gainsville because of the college but if you show your college ID you get like 10-15 more dollars than a regular person, and some classes will take it as extra credit. At least santa fe nursing school did.