Learn Hardcore French: D'habitude, Marie marche dans la rue et s'arrête au coin, près de la pharmacie. - Usually, Marie walks on the street and stops at the corner, near the pharmacy.

D'habitude means usually and is very common in everyday French. A slightly more formal synonym is habituellement; other options include en général, normalement.
Position: placing D'habitude at the start is very natural. You can also say Marie marche dans la rue d'habitude. Mid-sentence (after the subject) is possible but less smooth: Marie, d'habitude, marche… is more parenthetical.
Comma after a fronted adverbial like D'habitude is optional; many writers include it for clarity, so your comma is fine either way.

Why is it marche (walks) and not va (goes)? And how is marcher different from se promener?

marcher = to walk (the physical action of moving on foot). That’s what you want here.
aller = to go (destination-focused). Marie va would imply she’s going somewhere rather than describing the act of walking.
se promener = to take a walk/stroll (often leisurely). You could say Marie se promène dans la rue if you want the idea of a stroll rather than just walking.

Why is it dans la rue and not sur la rue or en rue?

In France, the natural phrasing is dans la rue for being out in/along the street.
sur la rue is common in Canadian French when talking about something located on a street (e.g., a house): une maison sur la rue X. In France you wouldn’t use it for walking.
There’s no idiomatic en rue for this meaning. Also note the difference: une rue (street, in town) vs une route (road, between towns).

What’s the difference between s'arrête and arrête?

s’arrêter (intransitive, reflexive) = to stop (oneself), to come to a stop. Example: Marie s’arrête au coin.
arrêter (transitive) = to stop something/someone. Example: Marie arrête la voiture.
To stop doing something: arrêter de + infinitif (or s’arrêter de): Elle arrête de marcher / Elle s’arrête de marcher.
To stop at a place: use s’arrêter à/au/chez: Elle s’arrête au coin. Using arrêter à for a place is not idiomatic.

Why is it au coin and not à le coin or à la coin?

au is the contraction of à + le. Because coin is masculine singular (le coin), you must say au coin.
For feminine nouns: à la (e.g., à la pharmacie).
Before a vowel or mute h: à l’ (e.g., à l’école).
Plural: aux = à + les (e.g., aux coins).

How does près de work? Why de and not à? What about contractions?

The fixed preposition is près de (near), never près à.
It keeps de, which contracts with articles just like any de:
- près du = près de + le (masculine singular)
- près de la (feminine singular; no contraction)
- près de l’ (before vowel/mute h)
- près des = près de + les (plural)
Examples: près du parc, près de la pharmacie, près de l’hôpital, près des écoles.

Is au coin enough, or should it be au coin de la rue? What about à l’angle?

au coin is fine in context; it means at the corner (implicitly of the street you’re on).
To be more explicit: au coin de la rue or with street names au coin des rues X et Y.
à l’angle (de) is a bit more formal/technical; it’s common in written directions: à l’angle des rues….
Don’t confuse au coin (at the corner) with dans le coin (in the area/around here).

Why use the definite article la in la rue and la pharmacie? Could it be une pharmacie?

French often uses the definite article for general locations where English might not: dans la rue corresponds to in the street/out on the street.
la pharmacie suggests a specific, known pharmacy (e.g., the one on that corner). If it’s any pharmacy, you could say près d’une pharmacie.

Any pronunciation tips for this sentence?

D’habitude: the h in habitude is silent (h muet), so you elide and link: sounds like “dabitude.”
marche: final -e is silent, ch = “sh” sound.
rue: French u is a fronted vowel; keep your lips rounded (not like English “oo”).
s’arrête: the ê is an open “eh,” and the final -e is silent; the t is pronounced. You naturally link to the next word: s’arrête au flows like “s’arrêt-o.”
au = “oh.”
coin: nasal vowel, roughly “kwenh” (don’t fully pronounce the final n).
près de: près has an open “eh”; the final s is silent. pharmacie: initial ph = “f.”

How would I make this sentence negative?

Standard written French: D’habitude, Marie ne marche pas dans la rue et ne s’arrête pas au coin, près de la pharmacie.
Note the placement around the reflexive verb: ne s’arrête pas.
In informal speech, many drop ne: Marie marche pas… elle s’arrête pas… (keep this for casual spoken French).

Why the present tense for a habitual action? Could I use the imparfait?

French present works for general truths and habits, especially with an adverb like D’habitude.
In a past narration about a habitual past routine, you’d use the imparfait: D’habitude, Marie marchait dans la rue et s’arrêtait au coin…

Why isn’t elle repeated after et? Is et s’arrête correct?

Yes. In coordination, the same subject can govern both verbs, so Marie marche… et s’arrête… is natural.
You could repeat the pronoun for emphasis or clarity: … et elle s’arrête…, but it’s not required here.

Could I replace the place phrase with y?

Yes, when the location is understood, y can stand for it: Elle s’y arrête (she stops there).
y typically replaces locations introduced by à, dans, sur, chez, en, and in practice it often replaces a whole locative phrase like au coin, près de la pharmacie once it’s established in context.
Don’t use en here; en replaces de + thing as an object, not a general location to which one goes/stops.

Is the comma after au coin necessary?

It’s optional. The phrase près de la pharmacie is an added detail about the corner; a comma sets it off nicely but isn’t obligatory. Both … au coin, près de la pharmacie and … au coin près de la pharmacie are acceptable; the version with a comma is a bit clearer visually.

Anything to watch for in spelling and accents?

s’arrête has a circumflex: ê. The related noun is un arrêt (also with ê).
près uses è (grave) and the final s is silent.
The apostrophe in d’habitude and s’arrête shows elision before a vowel or mute h.