• for temporary situations or actions that are only going on around the present
  *Water boils at 100° Celsius. <-> The kettle’s boiling
  It usually snows in January. <-> Look - it's snowing!*
  
  

But used for situations around the present with stative verbs
I like this wine. (Currently, this wine is what I like)
I believe you. (not in a general sense of believing, but the current utterance)

• for future references
  But used for timetabled events and in subordinate future clauses
  His train arrives at 11.46. I start my new job tomorrow.
  I'll kill anybody who touches my things.
  I'll phone you when I get home,

• to say how long a present action or situation has been going on
  I've know n her since 1990. (Present Perfect)

always, usually, often, sometimes, occasionally, rarely and never

days of the week: (+s if repeated) on Monday Tuesdays

parts of the day: in the morning, afternoon, evening

Some verbs are not often used in progressive forms.
I like this music, (not I’m liking this music.)

Many of these non-progressive verbs refer to

• states rather than actions.(e.g. emotional: like, hate, love)
• mental states (e.g. know, think, believe)
• the use of the senses (e.g. feel, see, sound, hear, smell, taste)

Can + sense verb/understand/remember implies progressive meaning
Can you smell something burning?

Occasionally 'non-progressive’ verbs are used in progressive forms in order to emphasise the
idea of change or development.
These days, more and more people prefer / are preferring to retire early.
The water tastes / is tasting better today.
As I get older, I remember / I’m remembering less and less.

Simple: used for the events - the things that happen one after another

Progressive: used for ‘background’ - things that are already happening when the story
starts, or that continue through the story.
There’s this Scotsman, and he’s walking through the jungle when he meets a gorilla. And the gorilla’s eating a snake sandwich. So the Scotsman asks…

Simple: used for the quicker actions and events (which are finished before the
sentences that describe them)

Progressive: used for longer actions and situations
Harris passes back to Simms, nice ball - and Simms shoots!
Oxford are pulling slightly ahead of Cambridge now; they're rowing with a beautiful rhythm

First I put a lump of butter into a frying pan and light the gas; then while the butter's melting I break three eggs into a bowl, like this

Simple: Regular point in time, not happening near the time of speaking

Progressive: The repeated action happening around the time of speaking
Actions happening around the Simple points of time At seven, when the mail comes, I'm usually having breakfast.
You look lovely when you're smiling.

Simple and Progressive forms can be used to indicate the same meaning
How do you feel? or How are you feeling?
My head aches? or My head is aching.

Simple: More formal form
More formal: I look forward to hearing from you.

Progressive: Less formal form
Less formal: I'm looking forward to hearing from you