This week, a medical team from Hospital Clínic has come to our faculty to collect blood from the students (or any other person around) who want to donate. I had never done it before, but due to a suggestion from a friend, I though "Hmm, why not? Let's try it.".
So I showed up there this morning. First of all, I had to fill in a form answering some questions about things that may make my blood inappropriate. Secondly, a nurse pricked my finger to see which blood group I have and also measured my tension. Then, I simply went inside another room, laid on a stretcher and waited while 450g of my blood were extracted. Afterward, I was offered drinks and food to eat... a lot (this was the best part ;).
After all, a nice experience. I think I will repeat it: I loose nothing (well, just an hour of time) and I might be saving a life! So, suggestion: go to give blood if you can.