My wife got a HTC Desire S at the weekend, and in 1 days she has used 50MB of data. She just downloaded a few apps, browsed FB and added her contacts.

As she is new to Android phones, how can we ensure that nothing else is on using data whilst the phone is idle?

That sounds normal unless she was connected via wifi then the data shouldnt be chargable

some were done using wifi and some via 3g.

is there a way of checking what background app(s)/processes are also eating data ie sync etc?

To be honest, you could easily have used 50MB just downloading apps and syncing your contacts - I wouldn't be too concerned about that. Do you not have a Wi-Fi connection available?

In answer to your question, though, I would probably leave the main things on such as Google Sync and Email Sync, as these use quite little data but their use outweighs what little data they use. Then it's just a case of going in to all the other apps, such as Facebook, one-by-one and adjust their Sync settings - either disable entirely, or set the Sync for a long period of time (eg. 6 hours). This will reduce the data usage.

If you want to go the whole hog and disable all data transfer, your best bet is to go Settings > Wireless & Networks > Mobile Data > (uncheck Data Enabled). But again, I would point out that the first day's usage is unlikely to be reflective, and to give it a few more days to see what your daily usage is actually like.

I use 3G watchdog pro to monitor my 3g data useage. Once it hits a pre-defined data limit, it will turn of the 3g connection for you (if you want it to). It also tells you which app used the data...very handy to spot a rogue app.

A handy tip, use wifi where possible - its 'free' and generally faster.

Be wary of things that are syncing in the background under the 'Accounts & sync' settings. When I got my Desire HD I found that Twitter/HTC Peep, Weather and HTC stocks were all syncing every hour and using a lot of data. HTC Peep was a real issue for me as it was using on average 50mb a day. My advice would be to turn off syncing of everything that you do not need or if you need it, sync manually.

Be careful of other apps that will update in the background too (e.g. Facebook) which sill automatically update every hour by default. Apps such as Sky News can be huge data hogs if they are set to update every hour too.

i will download this tonight and tell her to keep an eye on things

i do have wifi at home, but she decided to download games etc whilst i was doing the gardening and she isnt upto speed to technology!

thanks for the advice, i will check these things tonight

I am not up to speed on HTC phones but AFAIK on my ZTE Blade / OSF wifi takes priority over 3 g connections.

If you have your wifi turned on it should connect to this instead of 3G however this does put a drain on the battery, more so if the wifi signal is weak.

This is how the desire and Desire HD work. I am pretty sure all HTC phones work like this. I think there is a setting that you set, so this kicks in.

Leave wifi on and your phone will automatically reconnect to your wireless network when in range to any wifi networks you have used before. The phone will always use Wifi as a priority over 3g. For example i have wifi hotspots i use at work, home and my grandparents house.