The preceptors for the experience were great, explaining everything (which I'm sure was as easy as counting 1-2-3 for them, since this is probably the most basic thing they do in their careers) in as much detail as we could possibly want. Since I have pretty good veins (and am accustomed to getting needle sticks due to donating plasma), I ended up being a pretty good practice subject for my classmates.
What surprised me was what ended up being difficult about learning to draw blood. I always thought that getting the needle into the vein would be the hardest part, but it wasn't - at least not for me. It was much more difficult for me to find the vein in the first place, at least on people with no obvious veins. On top of that, holding the needle without moving it once it's inside the vein can also be a bit tricky. Connecting and disconnecting the vacuum tube without jiggling the needle and causing
We practiced with 22 gauge needles. The size of the needle actually decreases with increasing gauge number. The preceptor introducing us to the equipment mentioned that, as a point of reference, the needles used in donating plasma are 16 gauge, while the needles used in insulin injections are 23 gauge. To help clarify this, below left is a shot from when I donated plasma last semester after going through the Heme/Neo domain and getting curious about where "fresh frozen plasma" comes from, and on the right is the needle from yesterday's Phlebotomy session. Click to embiggen: