The more I listen to spoken French, which I am doing much more of lately, the more I see that liaisons are very often not used where I expected them.
My policy in the past has generally been to place a liaison nearly anywhere that an ending consonant led into an opening vowel or h muet, but this is clearly not what should be done -- I even see pas pronounced with no liaison, for instance.
I have heard from many users here that liaisons are often a matter of preference or may vary from region to region. However, I don't really know to what extent this is true, when it's optional and when it sounds weird, and finally what the effect is of using them or not.
By that I mean that in English, there are certain rules which are not formally required, but depending on your preference to observe them or not, lend different flavors to your speech. This seems comparable to me, and I am curious what effect the usage or omission of liaisons has on the sound of a French speaker's speech, to the ear of a native speaker.
As an example of what I mean, in English one might use who or whom, but very few people use whom and its usage would make you sound a bit more formal or educated. Likewise, lie and lay are separate words which people generally use interchangeably when referring to laying down or lying down, but this variation has no effect on how one sounds because they've blended so thoroughly that nobody notices the difference.