Sounding Like a Native Speaker - The English Pronunciation Reduction of -ing

I figured I'd make this post since I couldn't find much information about it on the internet.  Native speakers often take liberties when it comes to pronunciation. Often words or letters may be reduced for the sake of fluency and rhythm.  Recently, I spoke to a class about how Americans frequently reduce the -ing sound in the continuous form.

Example: 

I'm walking to the park. 

When spoken with the natural flow of native fluency, it becomes: 

I'm walkin' to the park.  

The -g gets dropped at the end of the verb.  Therefore, walking sounds like walkin'.  This is how many American native speakers pronounce verbs in the continuous form.  However, it's important to note this rule doesn't really apply in the case of gerunds, when nouns look like verbs with the -ing ending.

Example: 

Walking is fun.

In this sense, the full word is pronounced and not reduced.