When designing a board which uses parts you haven't used before, it always pays to very carefully check the footprint.
This same thing happened to a colleague who designed a very nice board only to find that what he thought was a sot-23 turned out to be a sot-323.
If you watch eevblog, you'll see that Dave Jones got caught with wide vs narrow soic packages in his nixie display project (also the tube footprint was wrong I think (and he had the tubes on hand!).
My bugbear is surface mount trimpots. I've managed to stuff them up several times :-(
There are so many footprints, and no component is available in all of them. Even if they were, your favorite supplier wouldn't have all of them.
I'm assuming that you're not building things in question measured in millions, and therefore you can't request a chip be made in a particular package. You're probably also not making things in quantities of tens of thousands, so you can't buy a full reel of whatever component you need. As such, you're in the position of only being able to source components in the packages that suppliers choose to make available in smaller quantities.
Having the components before you commit to a board, and physically placing them in a paper copy of your PCB can reveal all sorts of problems. Some PCB layout told will do this for you, but they can't check the actual component matches what's in their library unless they have a tight connection to your own or a suppliers inventory.