Good for you for doing this! I remember my first time in this too, and went on to be a 3+ gallon donor. I was anxious, but since my friendly boss was there giving too (he dragged me into it ) I was fine. We kibbitz.

Yes, hydration is very important. I would make sure to have a big drink of water or something before going to give. Keep drinking as much as you can afterwards. (Don't believe anyone who says you can only have 1 of their free drinks and cookies...sit and take as much as you need. I always needed the same amount of fluid as I lost.

If you feel a bit uneasy (stomach) during giving blood, ask for something to nibble on or drink. Sometimes the anxiety causes a person to not breathe deeply, to hold their breath etc and that will also make you feel lightheaded by itself. Holding your breath added to the fluid loss can do a double whammy on you.

You might also get your iron levels checked (by numbers) as you may have been good enough to give, but need to raise your levels for day to day anyway.

Try taking a magazine or book to read to keep your mind off the whole idea and sterile settings.

I am so proud of you! I found out I am CMV negative, and so they needed my blood for preemies. It always spurred me on to do it again and again. Maybe if you talk to the nurse or helper as you give, about what all it's used for, they always know the current greatest need etc, that will help motivate you too, and help you recover faster?