Present Simple vs. Present Continuous

Present Simple

I speak (or any other verb).
Negative: I DON'T speak
(short for DO NOT).
Question: DO you speak?

It's used for habits, things you regularly do, or things that do not change over time. 

It usually comes with the following adverbs:
Frequency adverbs: always, never, usually, normally, sometimes, often, hardly ever.
Every + period of time: everyday, every morning/Friday/week/summer/year.

Present Continuous

I'M speaking
(short for I AM).
Negative: I'M NOT speaking.
Question: ARE you speaking?
(am, is or are depending on the subject).

It's used for actions done right now, or in a close future, or during a short period of time. It's far more frequent in conversations than in texts.

It usually comes with adverbs such as: Now, today, tonight, at the moment, these days, currently.
This or next + period of time: this or next morning/evening/week/week/month/year/course/summer.

Exercise on Present Simple and Present Continuous