Although the built in software keyboards are great on almost every phone, there's just something special about the old school keyboards that we use on our PC. I mean, the software keyboards are excellent and get the job done fast and easy, especially if you need to answer a message quickly, but when you need to do some serious writing, the keyboards with physical buttons are a better choice.
The only thing you'll need besides the keyboard is the cable called OTG, which pretty much does all the job for you. This cable has USB 2 ports, from which you will be using both. The first port is the Micro USB Port that fits almost every smartphone on the market, so you shouldn't worry if your phone will be compatible.
The other port is an ordinary USB port that you will be using to connect almost anything, but in this case, that will be your keyboard. The process of connecting your keyboard and Android phone is pretty straightforward. All you need is to connect your keyboard to one USB port and your phone in another USB port. And actually, that's everything you need to do in order to use your keyboard on your Android phone.
There is a good and a bad thing when it comes to buying this cable. The bad thing is that you probably won't be able to buy it in the local supermarkets. The good thing is that it's really cheap, to be more precise it costs only $1, and since it is so small, you shouldn't be charged for shipping also.
Now once you've connected both keyboard and the phone, you may encounter some difficulties, and that difficulty is the keyboard layout. You can resolve that problem by downloading External Keyboard Helper from the app store. With this app, you can decide what layout you want to use, which is very useful.
The best thing is that you don't have to root your phone in order to connect and use the keyboard. Also, the connection process is as simple as it can get.