I used to just do whole blood, which is fairly quick and easy—just hook up and bleed into a bag—and can be done every 56 days.
Then I got into a habit of doing “Power Red”, where they hook you up to an apheresis machine, withdraw some quantity of whole blood, process it through the machine to separate components, then return most of the plasma and other stuff while retaining the concentrated red cells. In my experience, this usually takes a couple of complete cycles and part of a third, and then they end up with a double-unit of concentrated red cells. After that, you have to wait 112 days to do it again.
These days I mostly do double-needle platelets, so I’m going in every two weeks and getting a needle in each arm, then watching movies or TV or listening to podcasts for a couple of hours with my arms straight. Whole blood is withdrawn through one needle, processed by an apheresis machine, and then returned sans platelets with most of my other blood products plus some IV fluid. Using two needles allows for continuous apheresis during the donation, and they usually get 2-3 units of platelets, plus every few donations they also keep a unit of plasma. It’s possible to go back sooner than two weeks, but I like the regularity of this schedule.
I understand that not everyone is able to do this for various reasons, and I’m not trying to do any sort of self promotion because of it. I like that I’m able to help others by giving stuff that I’m making anyway (without any special effort on my part), even if the donor center canteen is no longer staffed with old lady volunteers serving sloppy joes: “Do you want pickles?” 
