Learn Hardcore Swedish: Jag vill att du skickar schemat till mig ikväll. - I want you to send the schedule to me tonight.

Here att is a complementizer meaning roughly that and it introduces the clause du skickar… after vill. You cannot drop it after vill: not Jag vill du skickar…. Also don’t use att + infinitive here: not Jag vill att skicka…. Use Jag vill skicka… only when the subject is the same as in the main clause (i.e., when you yourself will send it).

Why is the verb skickar in the present even though it refers to tonight (future)?

Swedish very often uses the present for future events when a time expression is present. …du skickar … ikväll naturally points to the future. It’s normal and neutral.

Can I say Jag vill att du ska skicka… or …att du kommer att skicka… instead?

…att du ska skicka… is common and fully correct; it can sound a bit more like an instruction/expectation.
…att du kommer att skicka… is a prediction-style future and is uncommon after vill; it can sound awkward because wanting a prediction is odd. Prefer plain present or ska here.

Why not say Jag vill att skicka schemat…?

Because att here would be the infinitive marker, but the subject of the action is du, not jag. When the subject changes, Swedish uses att + full clause: Jag vill att du skickar…. If you yourself are the sender: Jag vill skicka schemat….

Where does inte go if I want to negate this?

Two different meanings:

Not wanting the action: Jag vill inte att du skickar schemat till mig ikväll.
Wanting the non-action: Jag vill att du inte skickar schemat till mig ikväll. Inside the subordinate clause, inte comes before the finite verb: att du inte skickar….

Can I move ikväll somewhere else?

Yes. Neutral is at the end: …skickar schemat till mig ikväll. Other acceptable placements for emphasis:

…att du ikväll skickar schemat till mig.
Starting the sentence: Ikväll vill jag att du skickar schemat till mig. Avoid splitting the verb and its direct object in neutral style (so prefer not skickar ikväll schemat).

Why is it schemat and not schema?

Schema is an ett-word. Definite singular adds -t: ett schema → schemat (“the schedule”). Plurals: scheman (indef.), schemana (def.). Using schemat implies a specific, known schedule.

Can I say skicka mig schemat instead of skicka schemat till mig?

Imperative: Skicka mig schemat is common and fine.
Declarative (as in your sentence): …skickar schemat till mig is the safest and most natural. …skickar mig schemat is possible but less common with skicka than with verbs like ge.

Why till mig and not för mig or åt mig?

With sending, Swedish uses till to mark the recipient (direction): skicka något till någon. för means “for (the benefit of)” and doesn’t mark the recipient of a sent item. åt can mean “for/on behalf of,” and with skicka it’s unusual; stick to till.

Is Jag vill att du… too direct? How do I make it more polite?

It can sound quite direct. Softer request forms:

Kan du skicka schemat till mig ikväll?
Skulle du kunna skicka…? (even softer)
Skulle du kunna skicka schemat till mig ikväll, tack?

Why is it att du skickar and not att skickar du?

In subordinate clauses introduced by att, Swedish uses subject–verb order: att du skickar. Inversion (skickar du) is for main-clause questions or after fronted elements in main clauses, not after att.

Do Swedish verbs change with the subject (I/you/he…), like in English?

No. Present tense is the same for all persons: jag/du/han/vi/ni/de skickar; likewise vill is the same for all persons.

Any pronunciation tips for tricky parts?

skickar, schema(t): the initial sk-/sch- before front vowels is the Swedish sj-sound (like a breathy “sh”).
mig is usually pronounced like mej.
ikväll: stress the second syllable: i-KVÄLL.

Is ikväll the only correct spelling? What about i kväll? And mig/mej?

Both ikväll and i kväll are accepted; ikväll is very common in modern writing. mig is the standard spelling; mej is an accepted informal/phonetic variant (same for dig/dej).

How would I say it if I myself want to send the schedule to you?

Use the infinitive with the same subject: Jag vill skicka schemat till dig ikväll. Using att du skickar… changes the subject to “you.”