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	sudo dd if=[path_to_iso] of=[path_to_usb]

In my case:
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	sudo dd if=/home/slick/Downloads/debian-7.4.0-amd64-CD-1.iso of=/dev/sdb

IMPORTANT: Don’t provide path to the exact partition, for example:
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	sudo dd if=/home/slick/Downloads/debian-7.4.0-amd64-CD-1.iso of=/dev/sdb1

When you do that, you’re bootable pendrive won’t boot!

What dd command does? In brief explaination it will copy whole ISO content as a raw data into your USB.

After minute or two you should see something similar to:
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	1275904+0 records in
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	1275904+0 records out
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	653262848 bytes (653 MB) copied, 17,4742 s, 37,4 MB/s

Your bootable USB with Debian is ready to go.