1. Get A Great Lens.
Most people get so fixated on choosing the right camera that they forget about the most important part - the lens.
A camera with the most advanced electronics is useless if the lens, through which the light travels before it gets to the camera, is sub-standard. Unfortunately, most Micro Four Thirds (MFT) cameras come bundled with pretty cheap, all-purpose lenses which are aimed at absolute beginners.
The good news is that most manufacturers now have a selection of premium lenses which allow you to explore your creativity, improve your skills and take better photos. Buy your Micro Four Thirds (MFT) camera as a body only and then get a premium, fast lens to match your needs.
I particularly like prime lenses from from Panasonic, such as the Leica-branded 25mm f/1.4 Summilux. If prime lenses are not your thing, then check out the 12-35mm f/2.8 Lumix GX - it's a great walk-around lens and is a huge leap up from the standard kit lens options.
2. Don't Worry About Megapixels.
I'm going to say something radical here: the Megapixel (MP) resolution count is the least important part factor you need to think about when choosing a Micro Four Thirds (MFT) camera. Unfortunately most camera manufacturers still try to use resolution as a main selling point. It's mainly because they'd like you to believe the myth that more megapixels translates to better image quality. It doesn't.
I shoot family photography for a living on a pro-level Nikon D4 (which has 16MP), and I have never had a need for more. Most of the time, I wish for less because it would free up my hard drives significantly. It's very unlikely that you'll ever need more than 10MP. Which means that every new camera out there these days has more than enough megapixels for you.
3. Most Important: ISO and Autofocus.
You want a camera which can take photos in low light which means you won't have to put the camera away once the sun goes down (or have to ruin your photos with on-camera flash). And you want a camera that autofocuses quickly and without confusion - so that you don't miss the important shots.
Spend some time doing your research to make sure your camera excels at both of those things. I particularly like the Sony NEX-6 for high ISO tolerance; it has the same sensor as you'll find in a much more expensive camera - the Nikon's D700 DSLR.
Autofocus speed is pretty hard to compare when you're playing with a camera in a shop. I suggest you go online first and see what reputable reviewers have to say about autofocus speeds of different cameras you like.
4. Get A Body That Feels Nice.
A camera body, that is!
Beyond the sensor and autofocus, the only other factor you need to pay attention to when choosing a Micro Four Thirds (MFT) camera its exterior. And I'm talking about much more than its design. I suggest you go to a shop and play around with a few cameras which are on your shortlist, of course paying attention to the design (you have to look at it all the time, after all - and you want it to look nice). But also, pay attention to durability - we all hope that we never drop our camera, but the reality is that it can happen. So, does it feel like it's been well put together? How likely is it to survive a drop? Is the camera made from plastic or metal?
Have a look at the controls. Play around with them as if you were really about to take some photos. Do they feel intuitive? Are the menus easy to navigate? Are functions easily accessible through buttons or are buried in multiple, confusing touchscreen sub-menus?
5. The Most Important Factor.
A Formula 1 car is very useful to a skilled driver, but we all know that it's not the car that wins the race. The driver does.
Similarly, your camera doesn't create the photo. It just translates the story you see unfold into digital signals. The most important thing you can do to take the best photos with your new Micro Four Thirds (MFT) camera is to begin to look for stories around you that you'd want to capture.
Most people walk around with a camera in hand, asking themselves "will this make a nice photo?" I invite you to make a small adjustment to how you think, which will improve the photos you take with your new camera significantly.
Ask yourself, "what's the story here?"
A photographer is simply a storyteller who uses images instead of words to share stories of his subjects. The more you practice seeing the stories around you and translating them into imagery, the more amazing your photos will become.