Hi, me and two friends are heading to Melbourne on the 29th September 2016. This is a completely new experience for all of us, so any tips, help or advice would be amazing. We are going on a 1yrs working visa so does anyone know of best ways to find jobs, accommodation as trying to look at that before leaving and it seems quite tricky. Basically I'm a clueless girl looking for some direction.
Welcome to the forum, lottie.
Can I PLEASE suggest that you relax and not stress ... arriving and staying in Melbourne is no harder than going to Reading or Brighton ... really. Australia is comfortable, warm, fairly friendly, prosperous, and safe, and very similar to the UK.
There is not a lot you can do prior to arriving, but certainly bring copies of any qualifications you have, and certainly any references from former employers or bosses (especially their email addresses).
Once here ... the three of you should relax into one of the big hostels here in Melbourne, and just absorb the place for a week. You need to get a Tax File Number (TFN), and a local bank account, but other than that, not much to do.
I will suggest that after a week of orientation and induction, you will have met plenty of others in your hostel who can give you lots of advice. This is a good adventure, and you will have a great time ... the WHV backpacker scene here is pretty good (just stay away from the odd dipsticks, but you can pick those pretty easily).
And 29 September is a great time to be here - October through Christmas the Melbourne weather is great, and after that head for Sydney for New Year and January. Good luck!
And if you're a bit apprehensive about your first port of call ... perhaps stay at the YHA North Melbourne ... YHA hostels are safe and generally quiet all round the country ... the party hostels are more City, Fitzroy, and St Kilda. Another hostel recommended on here is The Nunnery - perhaps check its reviews as well.
You need to buy a Myki Card on arrival (like a London Oyster Card) - $6.00 plus whatever you put on it.

Sydney has a great fireworks show as CC suggests but you will struggle for accom already. You can get your TFN number once you start work but if you are looking at heading for regional work or such then perhaps get onto it when you arrive.
October-December is the wettest quarter in Melbourne on average (and apart from May the wettest months on average) so keep that in mind.
If you want to knock that bank account thing on the head you can set one up before you leave with options from some of the larger banks.
Having lived here since 2004, I can attest that October-December is not a wet quarter ... whatever the rainfall averages might indicate ... the weather is usually outstanding through the whole Spring Racing Carnival (mid October to mid November), and by about early December, it goes hot and dry.
Outside that, I agree that Sydney over New Year is hellishly difficult to book ... but not a real issue ... NYE in Melbourne is excellent as well. Mark raises an important point ... how you organise your year depends crucially on whether you're planning to do three months rural work in order to qualify for a second WHV year.

Bar work in the lead up to the Melbourne Cup at Flemington. I have heard it pays around $AU21/hour.
Lots of hostel, take less stuff with you than you think. All the brands are here for toiletries likewise shops such as Topshop here too.
Enjoy the adventure!

Thank you every one so much for your kind words they really have put my mind at ease. It's always nice to hear peoples point of view and it has given me things to think about so thank you again!
Went into Melbourne (the city centre) for lunch today ... the place is chock-a-block full of backpackers and other young people seemingly having a good time. You'll be fine. The place has a VERY strong Asian, Indian, and Middle East vibe ... all adds to the buzz.
In deed Lottie, weather in the Spring quarter can be glorious at times and also wet at times, averages just being that and perhaps an unsettled season it could be called though with Climate variation from one year to the next and from one decade to another, that can just make the saying about Melbourne true at times:" four seasons in one day " or if you do not like the weather on any particular day: " just wait a few minutes ".
It is best to wear lighter clothes in layers so you can peel one off as the day warms up.
One of the weirdest experiences I ever had in Melbourne was seeing a huge dust storm roll in from the north west and Melbourne Cup day which aside from Horses, drinking, fashion, partying and a female jockey winning it for the first time ever last year is renowned for Roses being brought to bloom for the Cup week and then if the weather turns, it'll be petals everywhere.
It i a great experience and if you want to go, look up the Cup website and see about booking a ticket at least several weeks beforehand if not as soon as you arrive.
If there are three of you, the total costs could amount to some $600/w in a hostel so considerable savings might be achievable if you look for a house share, plenty of web sites around if you search under houseshare or sharehouse etc., perhaps also checking out Gumtree.
You will find just about every hostel will have a noticeboard with jobs available but beware the dodginess of some and then if you want to look for work that will qualify you to apply for a second WHV, have a look at the Harvesttrail web site as that is a great guide of where farm type work is at various times of the year.
If the three of you are intending to stick together, once you are deciding to leave Melbourne, it is probably financially advantageous for you to buy a cheap car/van to hit the road with rather than all three of you paying for individual fares, again hostels and sites like Gumtree having adverts.
So make sure you all or at least one of you have a drivers licence and then another alternative for a trip between major cities is to do a campervan relocation, some on offer to be done for as little as a $1/day and three day/two nights allowed for Melbourne to Adelaide or Sydney and Sydney to Brisbane with a day or so longer allowed for longer distances and additional days sometimes available at a discount to normal hire so seeing as you are provided with your accomodation in a campervan, it can become an ultra cheap way of doing some travel.