If you're travelling abroad for anything more than a day or two, it really pays to have some sort of global roaming solution that's not just using your existing Australian mobile phone network.

Australian networks charge up to $15 per megabyte (MB), and a megabyte is a tiny amount these days -- enough perhaps to check your email or catch up on the news. 

But having Internet access on the go is incredibly useful -- for maps, apps, Skype, email, the Internet... everything that it's useful for at home and more.

Fortunately, it's it's really quick and easy to pick up a local SIM card for your iPhone, Android device, iPad or other smartphone. (BlackBerry users beware: the security used for BlackBerry email can make things go slightly wrong.)

Why shouldn't you get a local SIM?

There are a few people for whom it doesn't make sense to get a local SIM.

If you'll be travelling between countries every few days, it may not make sense to take out a local SIM in each country. There are some good regional options as excceptions to this rule, though -- Bridge DataRoam in Asia and the new "Euroaming" deals across Europe.

If your phone is "locked" to your home network, it won't work with any other network's SIM. Many phones sold on a contract and subsidised by the mobile networks are locked -- and the network will charge you to unlock it. Calculate how much you'll be using your phone abroad to figure out if the charge is a good deal.

If you'll need to receive calls and texts on your Australian number, that's not an option if you take out the SIM. 

If you need to connect multiple devices, consider a 3G-wifi router, which some people know as mifi devices. They suck down 3G data like a mobile phone and generate their own little wifi field so you can get online. There are several options for renting these, including from rental car companies! We've had great experiences with Tep and Droam  3G-wifi router rentals.

What do you need to do before leaving home?

Make sure the phone is "unlocked". Ask your mobile provider to confirm that you can take the SIM out and it will work with another network's SIM. (Test this with another Australian network's SIM in your phone before leaving the country.)

Record a temporary "I'm abroad, please email me" message for your voicemail. If you want to check in to your voicemail from abroad, there's a phone number and PIN code combination you can call.

Keep your home SIM card safe once you take it out of your phone. I like to tape the SIM card face-down (so the tape is on the plastic side of the SIM, not the metal side) to a business card and tuck it into my travel wallet.

Research telco options in your destination country here on Australian Business Traveller and elsewhere online. Feel free to drop a comment below or get in touch with us on Twitter if you have any questions!

What do I need to do when I arrive at my destination?

Know which network you're looking for, and whether there's a shop at the airport. Many international airports do have telco outlets, but sometimes (as at Singapore) they're in one of the bureaux de change or (as at London) the left luggage office.

Know roughly how much data you'll want to use. This is an inexact science, but for a week's email, social networking, maps, sending a few pictures and a bit of browsing, we tend to guesstimate somewhere over 100MB. Your phone will have a usage function -- reset it, check it after a week and extrapolate from there.

Then, find the shop you're after and ask the staffer to take care of everything for you. You're after a pay-as-you-go SIM card with data.

Make sure you know:

• the phone is working and the Internet's activated
• what the phone number is (consider adding an entry for "Countryname SIM" in your phone book)
• whether you can "tether" it to your laptop, or whether you can use the personal hotspot mode to create your own little wifi network if you want to 
• the four digit SIM card PIN code you may need in order to unlock the phone if you restart it
• how much data you have, and how to get more
• how to add credit to the phone if you run out
• what the helpline number is, and how to get through to an English speaking person
• how to swap your Australian SIM back into the phone when you leave

What pitfalls should I avoid?

Don't be stingy on the data. Better to pay $10 over what you think you'll need and not have to worry about whether you'll run out. (You'll agree when trying to add credit using one of those "press 1 for..." menus in a foreign language you don't speak.)

Keep the paperwork handy while you're using the SIM. Often, you'll overlook some crucial detail or code that's required, and it's useful to have the paperwork to refer to.

Don't lose your Australian SIM! Keep it safe somewhere, and know how to swap the SIM back to your Australian one (this'll usually require a paperclip, needle or pin).

Got suggestions for local SIMs? Know a nifty trick that we haven't laid out fully here? Or is there a hidden gem of a service that we've not yet unearthed? Share your thoughts in a comment below!