Well I was mostly prepared. They bagged it in a large bag and I put it in a styro cooler. The problem was that I didn't have a dechlorinator on me (that's the only thing I forgot). The fish made it home alive but the chlorine and chloramine really F*d up the poor fish. When I put it in my tank at home the chlorine had eaten away the slime coat, the gills were badly burned and the fish died like 2 days later.
I was surprised it made it as long as it did. One time I forgot to add dechlor. to a bucket when we were moving fish. The small ones went belly up as soon as they hit the water.