Can someone explain IVs to me?!

..was wondering if someone could explain to me the differences between gauge size

The larger the number, the smaller the IV catheter. A 22 gauge IV is much smaller than a 16 gauge IV. I'm sure it's different in every hospital, but the standard for our preop nurses is that a 20 gauge or larger is preferred. However, you have to go with what you get sometimes. Little old dehydrated ladies or someone who has been vomiting for an extended time may only have a vein that you can get that 22 or 24 gauge into, but it's still better than nothing.

and any tips or tricks you have when starting them? thanks!

Don't look for veins, feel for them instead. Veins will feel a bit spongy compared to the surrounding tissue. Even though you may see someone who will tear off the fingertip of their glove, it's best not to start this practice. You never know when someone has an undiagnosed blood-borne illness, and when you go to start on someone who has a known one, you'll be at a disadvantage if you have to do something different. Also, make sure you bring extra supplies with you. You might think you've got the perfect vein, get the catheter in, and realize it won't thread. Then, if you don't already have extras, you've got to leave the room to get more. And most importantly, don't be too hard on yourself! Starting IVs is a learned skill, and it takes practice.

Larger bore, smaller number. There are times that we need to give fluid boluses or blood products, and a larger IV lets that happen faster and with less hemolysis.