What can normal users do to protect sensitive content?

What can normal users do to protect sensitive content?

Given it's 2013 and we're thrown into the 'Post-Snowden' era, I'd like to
know
a) if there are simple yet effective measures that can be taken to protect
sensitive content/communication, where 'protect' basically means 'no-one
except the content producer and eventually the communicatee should be able
to read the content, ever'
b) if there is already a potential risk with the way the
content/cummunication happens now.
Here are a couple of examples of content/communication:
design documents etc now stored on Dropbox
code now stored on a private git server (basic ssh public key ath) and
also pushed to BitBucket
some stuff is stored on google Drive and SkyDrive as well
copies of all of the above reside on multiple machines, all with
unencrypted harddrives
copies of most of the above are also accessed by smartphones, so stored
there as well by the corresponding apps
sometimes sensitive information gets sent over SMS
mail is sent using a variety smartphone apps/webmail/desktop apps. The
apps connect through TLS (not even sure if that matters) but the mails
themselves are always unecrypted and using apps means it gets also stored
as plain text on a lot of machines (eg Opera mail stores a ton of mbs
files containing plain html of every mail)
from time to time we use a plain usb/firewire drive to pass content