If you use GPG, then use a 3072 bit DSA signature and a 4096 bit El Gammal public private key pair. Don't use RSA. I won't say RSA is broken by NSA or others, but Mr. Schneier warns against using commercial encryption products like RSA or PGP. Use FLOSS encryption whenever possible and use public ciphers like AES, DSA, El Gammal, TwoFish, Serpent, and Blowfish. Use public symmetric block ciphers more than asymmetric public ciphers whenever possible.
For the pete's sake, use full-disk encryption and encrypt your /home and /swap partitions using separate passwords for extra security. Use Novell AppArmor and learn how to use it. Create custom Novell AppArmor profiles for software applications that contain your online accounts and credentials like your web browser or your e-mail client.
Don't transmit anything sensitive in the clear to the Internet. Be wary of adding untrusted PPAs or software code from unknown sources.
If you must, use an anti-virus program like Comodo anti-virus for GNU/Linux. It won't catch the classified attack vectors coming from US DoD or NSA or CIA or FBI, but it will catch the other publicly known malware.
Above all else, try not to become a target of opportunity. Secure your computers and your data as tightly as possible so you can use them on any network whether it's private or public. Almost everything that goes to the Internet is public domain and it's fair game.