If you're life is stable enough that you can get decent meals before and after as well as decent sleep, its probably not too bad in the short term. Low fat food with high protein. If your blood check shows too much fat you won't be able to donate.

The anti-coagulant can make your lips tingle/go numb (usually not that big of a deal) while you're being drained. If you find that the tingling/numbness last longer than the procedure, over the counter antacids should reverse the anti-coag agent.

Having light skin and visible veins can make it easier for the technicians to successfully stick the needle in your arm correctly.

If anything feels wrong during the stick, let the tech know ASAP. You might not (probably won't) get paid unless the procedure completes, even when its the techs fault for sticking you wrong. So its best to have them try to reset the needle to be as comfortable for you as possible since you're stuck in one spot for at least an hour.

I usually felt like shit for the rest of the day after donating. I really needed to eat and sleep immediately afterwards but I also had an hour drive to get there and was in town to do grocery shopping, so couldn't.

I did it for about a year during the height of COVID until I kept getting repeatedly kicked for having one thing or another off with my blood. Unsure if there was actually something off with me or the plasma center had too many people wanting to donate and needed to keep the numbers down.