If you would like an alternative to Unetbootin for making USBs, Mintstick is a good choice. It's actually my preferred method. To me, it's the quickest and easiest to use. I've used it countless times, and it has always worked.
If you're unfamiliar with it, when you add it to your system, it comes as two separate apps. It won't be called Mintstick in your menu. The first app you'll want to use is the USB Stick Formatter...use it to format your USB before you write anything to it.
The second app is called the USB Image Writer. Use it to write your image to the USB after formatting.
Edited: Don't use the PPA. I'll explain in the following post.1. You can add the PPA and install it through the terminal by entering the following commands...
sudo add-apt-repository ppa:tsvetko.tsvetkov/trusty-backports
sudo apt-get update
sudo apt-get install mintstick2. You can directly install it (with the GDebi Package Installer) by downloading it from the link below. The latest build will be the last "all.deb" on the list.
http://packages.linuxmint.com/pool/main/m/mintstick/Either method will place it in your menu's Accessories category.