Common Layout For IOS And Android

Hello Community,

I want to develop an application for Android 2.3+ and IOS5+ devices.

I am a little bit confused how to create common layout of application so that it will work on IOS6 ,IOS7 and Android 2.3+ device.

What structure i should follow to develop application ?

What should i use to create common Layout "%", "dp" or "pixels" ?

Please suggest me.

Thanks & Regards

Jitendra Kumar