You should decide what type of front-end position you're interested to get into; the front-end is now so broad that it's tough to know everything.
First, prove you are proficient with the following:
http://learn.shayhowe.com/html-css/
http://learn.shayhowe.com/advanced-html-css/
Here's a contest today that can test your skills
https://a-k-apart.com
Learn javascript and show you know ES5 inside and out. If you already know ES6/ES2015, awesome, show that too.
Any project where you've written the code from scratch (not using Bootstrap), where you teach others what you did, will show you're on the right track.
Want to contribute to Github? Look for a language, project, framework, library you're interested in, fork the project and improve the code. Doing this regularly, every day if you can, will show you're eager to learn and contribute.
If you're already at this level, pick up a specialty. It could be templating within WordPress, .NET or Java, or it could be MVC based coding using React+Redux, Angular, or Ember. Pick your favorite from these, get super proficient and even blog about your progress.
Finally, once you've gotten this stuff done, you will set yourself apart by learning cutting edge tech like Service Workers, Offline first, progressive web apps and just about anything the Google Chrome Developers are talking about here:
https://www.youtube.com/channel/UCnUYZLuoy1rq1aVMwx4aTzw
My favorite is Totally Tooling Tips (all three seasons are gold).