I prefer the Google DNS servers (188.8.131.52/184.108.40.206) for faster DNS resolution. While the procedure to set it on Unity is trivial, setting it on LXDE needs little more effort.
- Edit /etc/NetworkManager/NetworkManager.conf and comment out the line starting with dns.
dns=dnsmasq to #dns=dnsmasq
- Edit /etc/resolv.conf and add the preferred nameservers before any other entries.
#Google nameserver 220.127.116.11 nameserver 18.104.22.168 #OpenDNS nameserver 22.214.171.124 nameserver 126.96.36.199
- Reboot and ensure the settings took effect.
$ nslookup www.google.com Server: 188.8.131.52 Address: 184.108.40.206#53 ...
This procedure is tested on Ubuntu 14.04 (aka Trusty Tahr).