I donated twice a week for almost a year (needed the money).
It DOES hurt, but not that much. I've seen grown men call out and I've seen old ladies not even flinch. A lot of your "stick" experience will depend on the skill of your phlebotomist and the size of your veins.
Drink a lot of water, at all times, not just on days you are donating. Keeping yourself hydrated makes your veins easier to stick and makes the donation process faster (your machine will run faster). Also doing daily curls with a weight will help you build the veins in your arms and increase your bloodflow (which makes donation faster). This doesn't take hours, 10 minutes a day makes a difference (especially if you do this right before going to donate).
Keep squeezing the ball during the removal cycles only (machine takes blood, separates the plasma, then you get blood back - Do not squeeze during the return cycle)
Every time I donated - I left that place STARVING. Bring yourself something or plan accordingly.
If you go and the place is busy - ask when their downtimes are. Or try different times/days. Sometimes it's quick and you're done in an hour (rarely), but usually you are waiting in line to get checked in, then a line to get a bed, then a wait for the phlebotomist to stick you, then you wait to get disconnected. I think my longest was 3 hours, but it was usually around 1.5 hours. Give yourself plenty of time before you have to be somewhere, because once you are hooked up you are there. (also I always use the restroom after checkin but before I get in line for the beds. You can't get up to use the restroom, so think about that before you try to drink all your water intake right before showing up to donate).