Tomorrow sees Apple’s annual launch of the new iPhone operating system, and this year’s edition, iOS 8, sees a host of new features and a continuation of the flatter, more minimalist design begun last year with iOS 7.

For many, the update can come as quite a surprise, with your iPhone or iPad getting an unexpected fresh lick of software paint, and minor frustrations inevitably vie with the new features.

Here are some of the features that you can look forward to, and some key tips on the updating process.

This year, Apple is putting a big emphasis on new health-tracking and fitness-monitoring features. Various third-party apps such as Nike+ and Runkeeper have seen the fitness app space explode in recent years, but with its new Health app, Apple is introducing “an easy-to-read dashboard of your health and fittness data”.

They have also created a tool for developers called HealthKit, so those fitness apps you already use can access the new features. Fitness tracking is also a tentpole feature of the Apple Watch, and is evidently something Apple is determined to make a key part of their ecosystem.

Another long-awaited feature is the introduction of third-party keyboards, previously prohibited for security reasons.

This has been an area where the far more flexible Android operating system has established a huge lead, and the move will see the introduction of huge numbers of alternative keyboard designs and technologies such as SwiftKey and Fleksy finally come to iOS. Typing on glass should get a good deal easier as a result.

Apple is emphasising its new “continuity” feature, which it promises will provide a seamless experience for those with multiple Apple devices – start an email on your iPhone and finish it on your Mac, say, or even answer a phone call on your Mac. This is hugely impressive in theory, but just as the promise of iMessage is undermined by its flaky implementation across multiple devices, it remains to be seen how smooth the continuity features are in practice.

New features A lot of the most advanced new features in iOS 8 are effectively behind the curtains, with Apple claiming it features “over 4000 new APIs to enable amazing features and capabilities”.

Chief among those is the introduction of “extensibility”, which changes the previous strict security limits on data sharing between apps and allows developers to greatly increase the way apps interact with the underlying OS – for instance, a photo app now has easier access to the photo library or add interactive alerts to the revamped Notification Centre.

Furthermore, apps can now avail of the TouchID sensor for inbuilt security within apps - that will make a big difference for security-focused apps such as the password manager 1Password.

Before updating, it’s critical to backup your device to your computer through iTunes – operating system updates are usually smooth operations, but the chance of something going wrong is not insignificant, so an up-to-date backup is vital to restore things to normal in a worst-case scenario.

While you might be eager to get your hands on iOS 8, or if your device is set to automatically update, the first day of release usually sees long download times as tens of millions of users refresh their devices, so if you can delay the gratification for a day or two, you can save yourself a good deal of frustration.

And if you’re using an older device, particularly the iPhone 4S or iPhone 5, it is prudent to hold off updating for a week or two – big software updates come with a share of bugs, and the older devices will struggle to keep up with the demands of the new OS until the kinks have been ironed out.

With last week's announcement of the larger iPhone 6 and iPhone 6 Plus, Apple was obviously playing catch-up in the screen size race, against Samsung in particular. Similarly, iOS 8 is closing some of the features gap that Android established in recent years, particularly with features such as custom keyboards, while extending its lead in terms of cohesive design.

It’s clear that iOS has outgrown the stark simplicity of its early days, when even an infant could operate it without much confusion. That’s a function of how the smartphone has grown to become our most personal computing device, and iOS 8 sees that power expand in new and potentially groundbreaking directions.