1. Design and build quality
Talking about design as your first consideration might seem superficial, but it's not just about the way the phone looks, it's about ergonomics. A super-shiny phone body might look amazing when it comes out of the box, but it won't have quite the same effect when it's got smudged fingerprints all over it, and more importantly, if it's not very grippy, you risk dropping it and ending up with a cracked screen. A sturdily built phone chassis has a better chance of surviving such falls.
Again, screen size is linked to usability. If you have small hands, you might not want a massive screen that you can't use one-handed. Having said that, if you're big on photography or watching videos then a bigger screen, like the super-wide display on the LG G6, might be the best option for reviewing your shots and comfortably catching up on your favourite TV shows. Screen quality is also important, with phones like the Sony XZ Premium sporting 4K resolution for the best possible images.
3. Great camera
As compact digital cameras have been gradually relegated to history, the smartphone camera has become more important. The ability to take shots any time and anywhere without having to lug any extra kit around is a huge bonus, especially as the quality of smartphone shots just keeps getting better. Though the cameras on top-tier handsets like the LG G6, iPhone 7 Plus and Huawei P10 are all impressive, they all bring something a little different to the table, so weighing up the pros and cons of their respective snappers is vital when choosing your next phone.
4. Headphone jack
When Apple dropped the headphone jack from its new handsets, it was a hugely controversial move. For those that are loyally wedded to their 3.5mm jack-toting headphones, it could be a deal-breaker. But it's worth noting that Apple provides small adapters with the iPhone 7 and iPhone 7 Plus, enabling you to plug your old headphones into the Lightning port. What's more, investing in a pair of Bluetooth headphones means you can cut out wires altogether.
5. Battery life
For most top-tier phones, there's not a huge difference in battery life with most needing a daily change. But even the ability to eke out a few extra hours is important with handsets like the Samsung Galaxy S8 Plus winning praise for their impressive battery specs. However, battery usage varies massively between users - those who watch a lot of videos are going to use up a lot more battery than those who use their handset to post the odd tweet.
6. Processor power
The processing power built into today's smartphones is pretty astonishing. All this new-found computer power is used to run web browsing, GPS, music streaming, videos, 4G connectivity and all the other scores of tasks your phone carries out on a daily basis. Looking for a phone with a powerful chipset inside is especially important if you're planning to use your phone for tasks that require a large amount of processing power, such as watching HD videos or gaming.
Once you've ticked off all the things you want to see in a mobile phone, it all comes down to price. While top-notch smartphones don't usually come cheap, it's worth shopping around for the best deals. Check out the O2 Summer Sale as a great starting point.