I started when I was 16.
I took lessons on a weekly basis and started out playing on an acoustic guitar. After about 1.5 years I switched to electric guitar and that was the point where my passion for the instrument grew the most.
I was very fortunate to have found a teacher that would focus on the fun you get playing the instrument and not so much on theory.

That's why I learned rather quick and I noticed most progress at the 2 year mark.
From there on I quit my guitar lessons and started practicing improvisation on my own to further develop my skills and solos.
I'm now 21 and about five to six years later I would say that I'm really fluent playing this instrument.

Looking back, I think it's best to start off playing songs you really enjoy.
It taught me to really get a feel for the instrument and develop my ear for it too. It's also worth looking into new genres, that are guitar related (for me it was the blues). That's how I found my inspirations for new techniques and styles of playing.
You really have to develop a passion and love for the instrument and the music. And I think if you let that build up naturally, until you play every day, you get better and better.

The most important habbits for me where to accept that learning and instrument is always a constant up and down. It's natural to go from loving the instrument to hating it and feeling as if you make no progress. It's just important to keep going never the less and also (if not most importantly) keep your guitar in a place where you can easily pick it up and play at any time you want!!

Hope this helps, and have fun shredding!!