Here is how I install Jekyll on my Mac, which should be mostly applicable to a Linux box. Jekyll is currently available in version 2.5.2, but I also previously tested this procedure for 2.4.0.

As a minimum requirement, you need to install Ruby (including development headers), and RubyGems, Ruby's package management system.

To make sure you install the version of Ruby needed by Jekyll, without interference with another Ruby already on your system, there is RVM, a command-line tool which allows you to easily install and work with multiple Ruby environments. Follow the instructions from the documentation to install RVM.

Once RVM is installed, you can install your version of Ruby (including RubyGems) by doing:

$ rvm install 2.1.2

Now, you can install the Jekyll gem (with all its dependencies) using RubyGems:

$ gem install jekyll -v 2.5.2
...
Fetching: jekyll-2.5.2.gem (100%)
Successfully installed jekyll-2.5.2
Installing ri documentation for jekyll-2.5.2
1 gem installed

You're set! At this point, you should be able to start getting the awesomeness from Jekyll.

Special note: In case you face specific issues, you can find answers in the troubleshooting section of the documentation site.

Using Jekyll

To generate a site, run the jekyll new command.

$ jekyll new mysite

Done! And you can check the newly created directory.

To serve the site locally, run the jekyll serve command, and then point your browser to http://localhost:4000.

$ jekyll serve

To build the site, run the jekyll build command instead. You can then take the files generated in the _site subdirectory and push them to your web host.