A common way of transferring an image, e.g. an operating system install image
or similar, onto an USB stick:

    # dd if=/path/to/input.file of=/dev/device

A nicer way to do this:

    # pv </path/to/input.file | sudo dd bs=8M of=/dev/device oflag=dsync && sync

On my systems, a block size of 8M seems to be a sweet spot, some 5-8% faster
than varying it in either direction. NOT setting the block size decreases the
speed of the process by at least order of magnitude.

When getting caught up in the first situation, watch the Dirty counter for a
rough indication:

   # watch grep ^Dirty: /proc/meminfo