For my first time, I tried a local yard for some oak - I called them, saying I knew nothing, and they were fairly helpful - said to email through the cutting list and they'd sort out boards to match. I added on 20% to each dimension (they then did the same), and then sent me a quote back. I went to pick it up (strangely had to do it at a particular time, I think 12-2pm), and had to wait around until they called my car through to collect. It felt a bit weird sliding 3 boards into my car when everyone else had flat-bed-truck-loads to collect! I second the comment about taking a saw - I barely managed to get my boot shut - 1 inch longer and I would have struggled to get home.
Given that it was for around £100 they were helpful, but I probably paid twice as much per cubic foot as I would have done for a very large order.