If you come home from a shoot with multiple memory cards full of photos, it can be tedious to import from each one in succession. But there's a way to streamline the operation so that you can do it in fewer steps.
If you're using a memory card reader that is capable of simultaneous importing--something like the Lexar Professional Workflow system or this [easyazon_link identifier="B00PGN5IM6" locale="US" tag="05060702-20"]Delkin reader[/easyazon_link], for example, it is possible to import from multiple cards at once using Lightroom.
You use the same importing dialog that you normally would. If you're using the micro importing screen, expand it to the full version.
Often, you would use the Devices section at the top. But for this, you don't want to use that because you can only select one device at a time.
Instead, find the cards in the list under the files section. Make sure the Include Subfolders often is checked.
And again, you have to get the right bit. If you click on the drive or device label bars, you'll only be able to select one at a time.
The trick is that you have to drill down into the folders. For each card, press the small triangles to expand so that you see DCIM for each one. Click on one. Then, holding down the Command key on Mac or CTRL key on Windows, select the next one so that they're both highlighted--just as you would for selecting multiple non-sequential files in other applications. Add as many as you need. In this rather extreme example I'm using here, I've selected files on a compactflash, SDXC card, and three microSD cards all together.
You'll see thumbnails from all the cards you've selected show up in the consolidated preview screen, and you can sort them or select them individually just as you would if you were importing from a single source.
Then hit import just as you normally would.
Lightroom treats it as a single import operation, so they all get the same treatment when it comes to import presets, metadata presets, and destination.