Do some quick, rough sums on a piece of paper so you have an idea of what things actually cost in Aussie dollars, for example $AUD1 = 10000 INDO Rupiah, $AUD5 = 50000 INDO Rupiah etc. Keep it in your purse. It only needs to be a rough conversion, this has saved me a fortune when my wife couldn't do the sums in her head while bartering with a Balinese wood carver - Bali boy of Darwin.
In Asian countries, take cash. The exchange rate is far better from an exchange shop than a bank and you remove the high withdrawal fees and low daily limits that the banks have in place to gouge you. I even take additional cash and convert to US dollars when I'm in Bali as it works out about 5-6 per cent cheaper. I now have a 'cheap' stash of US dollars for when the Aussie dollar goes south or I travel to the US - Greg of Wollongong.
You need to inform your bank of where you're going and how long you're going for. I've had my card suspended while in Italy as I forgot to inform them and it was flagged as a possible fraudulent transaction. It can take a number of days to get the card re-activated. I've also heard of cards being cancelled, in which case they can't just be re-activated and you'll need to wait for a new card to be mailed out - Mattah of Perth.
Walk a street or two back from the touristy areas and the price drops in half. Also, keep a note of local currency in your sock/shoe in case you lose your wallet. Better yet, don't carry everything in your wallet - do you really need the video store card in Prague? To save money on food, carry a small bowl with lid and plastic cutlery - you'll save on things like breakfast - but try and dine with the locals often. - Mt of Canberra.
Get a local pre-paid SIM card for your phone, store the numbers of your travelling companions local SIM numbers as well as the closest embassy number in your phone. Give your number to family back home. Forget the global roaming charges - Brendan of Canberra.
Ring your mobile phone provider to turn on phone roaming and make sure data roaming is turned off - Anna of Vic.
Get a traveller's credit card - this way you don't have to pay international conversion fees. Also, withdraw ATM money in larger amounts so you don't get charged ATM fees on multiple withdrawals - Sam of Sydney.
Cheaper is not always better. If your hotel is a 45 minute train ride from all the attractions it can pay to spend the extra $5-20 night a stay in a better location. You'll spend that on transport if you stay too far away. You'll also save your self a heap of time - Adam of Adelaide.
Take local currency and small notes, you'd be surprised how many taxis/vendors don't have change - Peter of Phuket.
Safety and security
Take mobile phone photographs of both the metro layout and local maps when you arrive. Tourists with paper maps are targets. Keep cards and additional money inside pants to minimise worry of being robbed of valuables - Matt Macks of Perth.
It may sound silly but take a whistle and carry it on you at all times. It will draw attention to you if you need help and is more effective than shouting. I was glad I had it when my tour guide in Vietnam pointed me in the wrong direction and I got lost. It was the whistle that he heard 1km away, not my shouting - Rob.