Sure, you can keep your phone with the same wallpaper, icons, home screens and settings that it had when you first bought it - but where's the fun in that?
A plethora of apps are available to enable you to get under the hood of your device and start making tweaks, and here we've collected ten of our favourites, from modding the notification lights and automating tasks, to revamping your home screen and managing files.
Our round-up of tools is slightly weighted towards Android because it's a more 'hackable' platform and there are more tools available for changing different parts of the OS.
If you're happy rooting your Android phone or jailbreaking your iPhone, then there are plenty of other apps and hacks you can consider, but we've restricted ourselves to tweaks and customisations that are possible without voiding your warranty. As ever, share your own recommendations in the comments.
Tasker lets you set up specific conditions (such as a time of day or a particular GPS location) and associate them with a related action (turning off Wi-Fi or muting your phone's sounds, for example).
The app recently received an interface overhaul to bring it into line with the look of Android 4.0+, and you can also use it to create customised menus and pop-ups. It's not the easiest app to get to grips with, but it enables you to automate a whole host of functions on your Android device.
Unless you're going to jailbreak your iPhone, you're somewhat limited in terms of the tweaks you can make to the interface and iOS settings. Launch Center Pro is one of the apps that can make a real difference, enabling you to create 'quick links' (like desktop shortcuts) to other actions within apps.
You can create a link to a specific option in Settings (such as Wi-Fi and Bluetooth), to the compose window for sending a specific friend a text, or to the 'take a photo' screen in Instagram, for example.
Android tries to do its best when managing your multi-tasking apps, but if you want to take charge yourself then enlist the help of Advanced Task Killer.
You can stop dozens of tasks with one calculated tap, add specific apps to an ignore list, automatically kill apps at certain intervals and free up memory for the tools you do want to use (some technical know-how is useful if you want to avoid closing system apps that you should keep running). Buy the £3.19 Pro version to remove the ads
If you're running Android 4.0+ Ice Cream Sandwich on your phone, then you can take advantage of Nova Launcher, a tool that's able to customise almost every pixel of the mobile OS's interface. Change colours, icons, dock behaviour, widgets and more as you like.
Upgrade to the £2.60 Prime version to get extra goodies such as unread counts and gesture control. It's one of the most comprehensive launcher tools on the market for Android, and you can back up and restore your customisations at any time should you need to.
Combine wallpapers, app shelves, icon templates and lock screens to create a look for your iPhone that is truly unique. Pimp Your Screen has an impressive number of templates to pick from, and you can combine resources from within the app with your own artwork to tailor your iOS device's home screens to suit.
There's a built-in preview feature so you can see the results of your customisations without exiting the app, and you can use the same settings across all of your iDevices if you wish to.
Available as both a free and paid-for app for Android, Light Flow lets you take control over your notifications and specifically the notification lights on your device. Install the free Lite version first, to check compatibility with your phone - Light Flow requires root access on some models but not others.
Once you're up and running, you can use the app to choose notification colours for certain apps and events, and even cycle through a series of colours if required. Vibration alerts and a special sleep mode can also be controlled by Light Flow.
Get hold of App Icons for your iDevice and you can switch between customised themes of icons, as well as build your own for specific apps or links to websites.
You'll need to have the apps in question installed, and only certain apps are covered by the templates provided, but you can radically transform the look of your iOS device with just a few steps. If you don't want to have to shell out any cash straight away, you can pick up a free version of the app that contains ads.
Dropbox works across computers, mobiles and tablets and has become much more than a file-syncing and back-up tool. So how does it help you hack your phone?
It creates an intuitive, simple file system for your device, it enables you to easily install apps from outside of the official stores, it gives you more options when sharing and attaching files in other apps, and more besides. Whether you want to automatically back up your Photo Stream on iOS or install a beta app on Android, Dropbox can lend a hand.
Zedge comes packed with wallpapers, themes and ringtones you can apply on your Android or iOS device - it's all free to download and use, and new content is added on a regular basis.
On iOS you'll find yourself limited to wallpapers for your home screen and lock screen, but the Android version extends this to cover audio features too, including notification sounds and other types of alert as well as calls and text messages. You can set wallpapers to automatically change based on a preset schedule too, if you wish.
Another of the many app launchers available for Android, Apex Launcher is one of the most popular and well-respected in this particular bracket.
As well as a customisable grid size across nine separate home screens, you can hide apps and on-screen elements (like the Google search bar), add animations and transition effects, and play around with the theme engine that covers icons and wallpapers.
Upgrade to the £2.59 Pro version and you can access more advanced features (including unread count notifications) and additional gestures.