It's quite astonishing how many film, music and interactive events the SXSW festival in Austin, Texas, manages to pack into nine days. Last year the music section of the event – created in 1987 with the aim of fostering new ideas and bringing creative types together – featured more than 2,000 acts, including headliners Bruce Springsteen and Jay-Z. And with the likes of Wavves, Nick Cave and Major Lazer at this year's event, from 8-17 March, Austin remains a vital destination for music fans.

Yet the festival can be overwhelming for the first-time visitor. While industry professionals lap up new developments across the music, film and technology sectors, the sheer number of shows, events and lectures can be intimidating to the casual tourist looking to have fun in the "live music capital of the world".

And high prices for tickets, or "badges", as advertised on the SXSW website, can be a deterrent. Once you've stumped up the money to get to Texas in the first place, who can stomach another $1,000 for a platinum badge giving access to all the music, film and interactive events? Even more moderate ticket options, such as a music-only badge, cost around $600. So why do throngs of music lovers return every year?

What's been something of a secret to Austinites for years, but which others are now discovering, is that it's possible to enjoy SXSW without paying a dollar. You can eat, get drunk and see thousands of great bands for free. I didn't quite believe this until I attended my first SXSW Unofficial Showcase last year.

Arriving in Austin ticketless and with low expectations, I asked around for the best places to go. On the advice of an Austinite friend, I went to The Parish (214 East 6th Street, theparishaustin.com), where National Public Radio (NPR) was hosting a free "unofficial" party on the first day of Music week. I arrived early and, to my surprise, was greeted at the door with a tequila shot, two beer tokens and a taco.

I washed down my complimentary lunch with the beers and was promptly tapped on the shoulder by a couple of bubbly PR staff, who proceeded to offer me as much rum as I could handle. Hazy after a couple of shots, I was then targeted by another rep, who convinced me to try some of the local ale – just as The Magnetic Fields began to soundtrack my childlike delight at the free pleasures on offer.

A few more free drinks later, I vaguely remember stumbling out of The Parish, naively raving to my friend – an SXSW veteran – about the free booze and food, and the high calibre of musical acts. It was then she let me in on the secret: "Just stick to all the unofficial parties and screw paying for tickets – hardly anyone in Austin does." And so my week of complimentary hedonism began.

I continued to consume free beverages, acquired a surprising number of sunglasses, ate a lot of tacos and, most importantly, managed to catch a lot of great bands including SBTRKT, The War On Drugs, Beach House and Deerhoof among many others. Held in the daytime hours of SXSW Music week, the free unofficial parties have, in recent years, become as popular as the ticketed evening events. This is partly because big money companies use the shows to promote products. Brands such as Converse, Miller, Spotify and hundreds of others attempt to throw the best parties and – inevitably – give away lots of free stuff. Admittedly, this has led to the festival becoming increasingly corporate, and for some it has certainly lost a degree of its indie credibility.

But there is no denying the appeal of these corporate-sponsored shows. In the past three years, some of the unofficial parties have even featured headliners such as Jack White and Kanye West. Last year A$AP Rocky showed up to entertain at the small-scale events, held in various nooks and crannies in the city.

So, given that none of these parties is actually advertised on the official SXSW website, how do you find them? Social media is the answer.

Tweets and posts begin pinging back and forth in the weeks leading up to most of the free shows, generating a buzz on influential music blogs such as do152.com. Websites such as showlistaustin.com and Facebook groups such as Unofficial SXSW Guide and the SXSWPartyList focus on listing the unofficial events.

Quite often you have to RSVP to the parties online, which means the companies will add you to their mailing lists in return for providing complimentary entertainment for the day. If that sounds too much like hard work, pay $40 (which, let's be honest, you'll probably make back in about an hour's worth of free drinking) and rsvpster.com will get you entry into almost all the free parties, and provide a spreadsheet detailing who is playing, who is sponsoring and any rumours of secret performances.

With the unofficial parties becoming increasingly popular and, in some cases, overblown, one may think they could begin to pose a threat to official ticket sales. But the music, film and interactive elements of SXSW have such a reputation with industry professionals that these tickets will always be bought by bigwigs.

It is also inevitable that some of the bigger headliners (such as Jay-Z and Bruce Springsteen last year) will simply refuse to play the daytime shows and keep themselves under wraps for the ticketed events. But still, for the music fan on a budget or a first-timer weary of pricey festival badges, it is definitely worth heading to Austin and signing up for the unofficial parties. Free music? Free beer? Free tacos? And it's usually sunny too? You can count on my RSVP.

• Festival details at sxsw.com. Flights from London to Austin over festival dates from £540 at kayak.co.uk. For advice on accommodation use our Austin city guide