The first time I picked up a guitar I did not even know that it had to be tuned. What I played sounded horrible but I was just a little kid and I had my fun nonetheless.
Most guitars have been crafted by luthiers (guitar makers) to have 6 different sized strings. And it is so easy to get the guitar out of tune, just by traveling the strings give into the temperature changes and have to be tuned again by the time you are ready to play. Even just slightly touching the tuning keys or leaning the neck of the guitar against a chair for support might get it out of tune. But for a musician tuning is not a problem, one might even switch from the standard tuning to the myriad of tuning alternatives.
So whatever tuning you desire to choose you need to either ask a friend, train your musical ear, rely on gadgets or just use an app on your smartphone.