Can you halve your mobile bill? The flood of new handsets, Samsung's S5 being the latest, makes many think it's all about the tech. It's not.

Choosing a mobile is like choosing a car.

Don't just think of the upfront cost, it’s the year on year costs that can cripple.

Yet if you know what you’re doing, many can save £100s. Here are my need-to-knows

Do you pay more than £15/mth?

This is the key benchmark price, for the simple reason that the cheapest UNLIMITED minutes, texts, and a decent 2GB of data Sim-only deal costs that. So if you pay more each month, unless you’ve extremely high data usage, or paying for a flashy handset, you need to ask yourself why.

And you don't have to change your number, you can take it with you.

Match your exact use to your tariff

If you’re on a mobile contract, the aim is to perfectly match its inclusive minutes, texts and data to your usage. Underuse tends to mean you're overpaying on the monthly fee, overuse usually means you're paying too much for any additional minutes, texts or data. To help you do this www.billmonitor.com logs into your online mobile statement, analyses your bill and presents its top pick tariffs on the back of that.

Switch to uber-cheap Sim-only deals

If you don't need a new handset, the best deals come from just switching Sim, provided you’re out of contract.

- Cheapest pay-as-you-go: For all but very low users www.Giffgaff.com which piggybacks on the O2 network is very competitive. It’s pay as you go but offers contract-style bundles without the contract. So for £7.50/mth you get 200mins, unltd texts and 250MB right up to £20/mth for unltd texts and data, plus 2,000 mins. It’s worth noting it’s not 4G (the fastest mobile broadband standard) yet.

- Cheapest Sim-only deal: If you go to www.virginmedia.com/mobile and tell it you’re not its home phone customer (unless you are) it has my top pick all-rounder deal with unlimited mins and texts, plus a decent 2GB data for £15/mth. Virgin piggybacks on the EE network.

It’s worth noting some handsets are locked to one network's Sims. If your new Sim isn't on the same network (or piggybacked on it), then you'll usually need to unlock it. This can often be done at no cost with a code. Full help at www.mse.me/unlockmobiles

Hot iPhones & Samsungs

For the brand new Samsung Galaxy S5, the thing you rarely hear is the cheapest route for most is to buy the handset unlocked upfront (its £529 from GiffGaff and £570 elsewhere) and then just use a cheap Sim-only deal. If you can’t shell out upfront see my Cheapest Samsung Mobiles Comparison Tool at www.mse.me/samsung.

I can't do Samsung's yin without Apple's yang. Again though, the key route is buy the phone straight (5S 16GB is £570 at Carphone Warehouse) and use a Sim only deal. If not then try my Cheap iPhones Comparison Tool at www.mse.me/iphone.

Haggle down your contract

If you don't want to switch, and are near or past your contract's end, you're carrying a powerful weapon... your loyalty.

The mobile world's a mature market. Everyone has a handset, so networks fight hard to win custom from elsewhere and keep their own. So if it won't give you a good enough deal, let it know. The aim's to get through to 'customer disconnections', which internally is often called 'retentions' as its job is to keep you. That's often where the corking deals come - it works.

Last Nov, I polled users of my site who'd tried a haggle – most succeeded. A huge 73% of Virgin Mobile customers succeeded, 67% of EE, 65% of Vodafone and 63% of Orange and 62% of Tesco Mobile.

Here’s a recent examples of how well this can work: Forumite ELFY: "My Orange contract was up, so I asked what they could do for me. I rejected two offers until I got £16/mth, for 1.5GB data, unltd texts and 2,000 mins. A saving of £36/mth - that's £432/yr."

And one of my team, MSE Jenny took the ante up a bit, "My £12/mth Orange deal expired, so the price went up to £29/mth. I called to say I wanted to leave, and was transferred to 'disconnections'. They called my bluff, saying 'Fine, you'll be cut off in May'. So I called theirs and said 'OK'. The next day they called back, offered 500 mins, 500 texts and 600MB for £6/mth on Sim only - a corking deal."

Insure the whole family's smartphones for £10/mth

Most networks charge around £10/mth to cover one handset, but it's possible to cover ALL family smartphones for that.

The trick is switch to www.nationwide.co.uk FlexPlus which charges £10/mth (so £120/yr) bank account, which includes cover for the whole family's mobiles (max £1,000 per phone), provided you all live together and the children are under 19 (or 22 if in full-time education). It also gives worldwide family travel insurance (max age 74) and European breakdown cover for the account holder.

If you just want the cheapest standard policy, my best-buys are at www.mse.me/mobileinsurance