Present Simple or Present Continuous?

General truths:

• Water boils at 100 degrees.

Actions in progress at the moment of speaking:

• The water is boiling now, so you can put in the pasta.

Permanent or near-permanent situations (true for several years at least):

• Marina lives in London.

Temporary situations:

• Marina is living in Paris for a few months (usually she lives in London).

Situations that are gradually changing:

• I'm getting better and better at speaking English.

Habits and regular actions:

• I drink coffee every morning.

Temporary or new habits:

• I'm drinking too much coffee these days because I'm so busy at work.

Annoying habits (usually with 'always'):

• My flatmate is always leaving the kitchen in a mess!

Future events fixed by a timetable:

• My plane leaves at eight tonight.

Future reference after 'when', 'until', 'after', 'before' and 'as soon as':

• I'll call you when I get home.

Definite future arrangements:

• I'm meeting Daniel after class today.

Narrating the plot of books, plays and films:

• At the end of the book, the detective catches the killer.

Describing people in pictures and photographs:

• In this photo, my mother is walking beside a lake.