Mandarin: when is it okay to use only 點 instead of 一點? 一點 means "a little" when applied to adjectives. For instance, 快一點 means faster (i.e., fast a little) but often times people shorten 快一點 to 快點.

What is the principle for shortening 一點 to 點?

Can you always shorten it, or does it only apply to certain words like 快? 
For example can you say 淨點 instead of 淨一點? or 吃點?

Is it only colloquial, or can you also shorten it in writing as well?
點 「吃點東西吧！」、「一點小事別在意！」

一點 「也少盡一點子心哪。」

一點點 「祇有一點點大。」

一點兒 「大意一點兒」

In most cases these are interchangeable.

We do not omit 一, if there is no verb, adjective or adverb in front of it. 
For example, 一點小事別在意！