With 'n', your tongue touches the back of your teeth. With the 'ng' as a suffix to another word, such as in the article "ang" (meaning 'the'), you pronounce it like you would the end of 'gang' -- pushing the breath/sound out of your nose and with the tongue suspended midway in your mouth. Haha! Sorry if that explanation is a bit elementary as I'm not a speech coach. If the 'ng' is a standalone word, such as when it is used to mean "of" (example, anak ng meyor, "son of the mayor"), 'ng' is pronounced as 'nang.' However, the 'a' sound is NOT like the one in 'gang,' but more like the short 'u' sound in the word 'lung'. Hope this helps. :D

Try to say sing-a-long.. Then separate the sound /nga/