I'm going to take a stab in the dark here, but I am willing to bet everyone who reads this has some sort of smartphone. If not, then you probably have some sort of tablet.
Each of the big 3 has an offering in both the smartphone and tablet avenues. Each has their own marketplace/app store/play store. If you're like me, you have your fingers in each of these ecosystems.
Admittedly, my presence is more in the Microsoft ecosystem than Android or Apple, but I am not confined to just Microsoft. If you're like me, you might have a phone as one system and a tablet on another. Or maybe you have more than one phone and/or more than one tablet.
My train of thought is that it is better to be well versed in multiple platforms than it is to be a master of one. Why do I believe that? Because if you invest all your time into one platform, you will be setting yourself up for disappointment when the world changes and you are no longer able to get that product (read: BlackBerry in another year). Unlike ancient coding languages, having a skill in an outdated system will do you no good on these devices.
So, how do you live unattached? In reality, you can't. You have to anchor somewhere so that you can explore. But its best to keep that boat in top shape so that you can pull that anchor up at any time an sail to another port.
How to keep your life transferable. Keep your investment in apps to a minimum. Why? Because the more you invest in an app ($$$) the more you lose if you ever have to switch (-$$$). In most cases you can keep your app use to free apps (like the best things in life, most of the best apps are free!), but if you ever have to buy an app make sure to keep the e-mailed receipt. If you don't get those receipts, make sure to opt in for them. Then on whatever e-mail address, filter for those app receipts, and send them to a specific folder in your e-mail client for safe keeping. Should the need ever arise for you to jump systems, then you will be prepared to recover your purchases.
Having those receipts will provide proof of purchase. Most app developers are 1 man operations, or they have small teams. find the developer's website (if it exists) and send them a friendly e-mail detailing that you love their app and were hoping to have your license on the app transferred to your new device. Ask them if it is possible. Developers love challenges (otherwise they wouldn't look at pages and pages and pages of code all day long), so they may be inclined to take up this challenge and see how they can switch your license over. And if not, they may just give you a license for the new system. And if you're realllllly lucky, you can possibly get your data files transferred/converted too!
Biggest takeaway from contacting the developers? Don't be a jerk. Nobody wants to deal with a jerk. I know we've all been advised that you should demand what you pay for, but this isn't a restaurant. You're not seeing these people face to face. You've got to stroke their ego (compliment the app), detail your situation (hopping platforms), and ask if your desired results (getting app on new platform) are possible. Being a decent human can go a very long way.
My best suggestion for being modular in whatever device you use: Learn the settings. Every device has a settings menu, and the biggest problem for users is that they are not able to get their device to do exactly what they want. In most cases, almost all of the configuration can be found in the settings menu found on the OS level, but sometimes you will need to open specific apps to dig deeper. Having toyed with all 3 systems quite a bit, the settings menu is my biggest complaint on all 3. It seems that nobody has a good grasp on an intuitive way to organize the settings menu. You can scroll down the options and go from Bluetooth settings to screen lock to wifi to ringtones to display brightness. Almost none of them are consistent and logically organized.
Knowing the settings menu makes you a valuable asset for many of your friends, coworkers, and relatives. And sometimes, knowing settings will get you into favorable situations (promotion, romance, and food... I've got them all from fixing people's settings. Yeahhhh baby!). My biggest pet peeve in settings is on iOS devices (pre-iOS 7... I haven't had to change a setting for anyone on iOS 7 yet). The settings icon can be placed anywhere on any screen, and if not on the screen, then it can be hidden in a folder. I tend to spend the most time looking for the icon (and yes, I know I can type settings in the system search, but I usually don't try typing in front of others because I have fat fingers... and I'm a little sensitive about them. Don't judge me). On Android and Windows phones they can be found in consistent locations. For Windows Phone, go to the home screen and swipe left, find settings in the list of apps that are in ABC order. For android Phone, swipe down from the top of the screen, the top right icon should be the settings button. If you have an older android device you may have to find settings in the all apps menu. For Windows 8 based tablets, swipe left from the right edge and select settings.
The biggest thing on each is knowing how to navigate and some of the tricks to make efficient use of your device. Getting to know these things is only a matter of time spent with the device.
This whole article came from my mind. I wrote it because, I have a friend who is the biggest Apple fanboy I know. He recently bought a Lumia 1020 because he was enamored with the 41 MegaPixel camera on it. That was enough for him to want to test it out. He decided to give it a couple week trial run, traded in his iPhone 5 for cash and bought the 1020. He loved the interface, became highly infatuated with how well the phone worked and the customization of the tiles. Then it hit him, he is a very app centric person. Things that he normally relied on doing in a regular day were not yet available on the Windows Phone platform. His biggest hole was no box.net app. There were other minor missing apps for his use, but for him it was a deal breaker if he couldn't get to the files he has in his box account. So, iPhone 5S came out and he returned the Lumia 1020, paid the $35 restocking fee, and bought the 5S. He said if he couldn't get the 5S he wouldn't have been too disappointed, because he definitely felt he could make it work. But he was heavily invested in an app he couldn't get on the phone he really wanted (he still writes about how he misses the camera, the screen size, and other Lumia features).
That brings me to my final point. If you're using apps (like cloud storage) for important daily activities, try to utilize a service that is available across each of the big three. Microsoft has done good work with making their services available to all devices (Skydrive, Xbox Music, Smartglass, Office), but there are plenty others who are available on all 3.