The n of Spanish has three sounds, which are determined by the sound that follows. Two of the sounds commonly appear in English in much the same way, and the third one does occasionally.
The most common sound for the n is similar to the "n" in words such as "nice" and "dance." For Spanish speakers, the tongue may be a bit farther forward than what it is for many English speakers, at the top of the teeth rather than on the ridge between the teeth and the roof of the mouth.
When the n is followed by an f, m, b, v or p, it has the same sound as the m.
This phenomenon occurs in a few English words during casual speech. One of them is "input," which is often pronounced the way that "imput" would be.
Since the n is pronounced as an m when an m follows it, in effect the n becomes silent. Thus, for example, inmigración is pronounced the same as if the word were imigración.
You might observe that many English cognates of Spanish words where the n has the m use the "m" in the English version. For example, énfasis is the equivalent of "emphasis" and inmenso is the equivalent of "immense."
Note that the following sound doesn't have to be in the same word as the n, only pronounced immediately afterward. So con permiso is pronounced the same as compermiso would be. This running of words together, where the sounds of one word affect those of another, is known as elision.
The third sound of the n occurs when it is followed by the k or g sounds. Note that the k sound can be spelled using qu or with a c that is not followed by an i or e. The sound in these cases is much the same as in English when the "n" is followed by the same sounds, in words such as "single" or "sink." Note that in these words the tounge doesn't touch the front of the mouth, and the sound comes from the back of the mouth as it prepares to pronounce the following sound. Thus the "n" of "bank" and the n of banco are similar.
In our brief audio lesson on the n you can hear the phrases "buenos días" (good morning), "lo siento mucho" (I'm very sorry), "con permiso" (excuse me) and "encantado de conocerla" (pleased to meet you) and the word inglés (English).
The sound of the n should not be confused with the sound of the ñ, which is a separate letter of the Spanish alphabet.