Heads up notifications, in case you didn’t already know, are an experimental type of notification that can be found in 4.4.x versions of Android. They aren’t openly available to use on an unmodified ROM, but many custom ROMs will have this feature enabled by default. As always, the Xposed Framework can be used to enable the feature. There are also third party applications available to activate heads up notifications as well.
While there’s no shortage of quick and easy ways to enable these notifications, knowing how to do something from scratch is never a bad thing. As such, XDA Senior Member moonknightus has provided a pretty comprehensive tutorial on how to make these modifications manually. The tutorial is quite useful as it seems that simply enabling heads up notifications caused several issues that effectively made it unusable and some of the steps described should address those issues. The guide is geared towards the Sprint Samsung Galaxy S3 running an ND8 Kit Kat firmware. However, using the information provided, it may be possible to get the desired result on other devices or ROMs. There are indications within the thread that this method can indeed be transferred to a variant of the Galaxy Note 2.
The process is fairly straight forward and accomplished by using a combination of apktool and your text editor of choice to decompile and modify the code contained within the SystemUI and SecSettings APK files. Once the changes have been made, you can push the files back to your device and enjoy your new notifications. Some previous experience with decompiling and editing system files would be a great help but this is also quite a good and straight forward project for someone keen to learn how to do this sort of thing.