Hacktoberfest is a month-long celebration of open source software run by DigitalOcean. Hacktoberfest is open to everyone in our global community Five or more pull requests must be submitted to public GitHub repositories. You can sign up anytime between October 1 and October 31.
It is open to everyone. No minimum requirements at all. All you need is a good understanding of git and github.
Go to this link . Hacktoberfest and register with your github account.
Once your registered you can find the search issues with hacktoberfest tag and Start solving it.
Now comes interesting part WHAT WILL YOU GET AFTER PARTICIPATING??
So the answer is you get free limited T-shirts.
Also even if you don't qualify for the T-shirt they send the stickers by mail.
So here is the summary :
So start contributing and get the free t-shirts....!!