First things first:
a) do you already speak, or have a basic knowledge of, Gujarati?
or (b), are you planning to learn Gujarati and want to write from the start?
If (a), then you need to learn the basic Devanagari layout on a ‘qwerty’ keyboard. Gujarati is one of the languages that use an adapted form of the Sanskrit or Prakrit alphabet: others include Hindi, Punjabi, Nepali, Bengali, etc. Once you have learned the basic layout, you can apply to any of these languages.
ગુજરાતી “Gujratii” is the result if you type the following on the ‘qwerty’ keyboard: i-g-j-e-l-r. Obviously, this bears no resemblance to the Gujarati, but that is how the Devanagari letters are mapped to the ASCII codes.
The font: if you are using Windows, all these Indian fonts are available, already built in to the system. Accessing them can be a bit of a nightmare, but it is possible. I have over 35 different fonts I regularly use, from Hindi, to Korean, Arabic, Chinese, and Thai. I am planning to put an open-source web page on-line soon to help all those budding linguists. Till then, contact me at .(JavaScript must be enabled to view this email address) and I shall try and help you.
An interesting site is the following also: http://www.omniglot.com/ (I think!) contact me and I can give you more details.