Learn Hardcore Chinese: wǒ yào chī mǐfàn.

Desire/intention: 我今天要吃米饭。 I want to eat rice today.
Planned/near future: 我待会儿要吃米饭。 I’m going to eat rice in a bit.
Obligation (less common with 吃米饭): 你要按时吃药。 You must take medicine on time. Tone and context determine the nuance.

What’s the difference between 要 (yào) and 想 (xiǎng) for “want”?

想 is softer: “would like to,” a wish or inclination. 我想吃米饭。
要 is stronger: “want to,” intention or decision. 我要吃米饭。 In service contexts, 我要一碗米饭 is a normal way to order in Mainland Chinese. If you want extra politeness, use 我想要/我想吃/请给我…

Is 我想要吃米饭 acceptable?

Yes, 我想要吃米饭 is acceptable, but many speakers prefer the simpler 我想吃米饭. Use 想要 more often with nouns: 我想要一碗米饭 (I’d like a bowl of rice). With verbs, 想 + V usually sounds more natural.

How do I negate this sentence naturally?

Common options:

Lack of desire: 我不想吃米饭。 I don’t feel like eating rice.
Refusal/stronger: 我不要吃米饭。 I don’t want (refuse) to eat rice / Don’t give me rice.
Prohibition (telling someone): 不要吃米饭。 Don’t eat rice. Avoid using 没 to negate desire here; use 不想 or 不要.

How do I turn it into a question like “Do you want to eat rice?”

Several ways:

Yes–no with 吗: 你要吃米饭吗？ / 你想吃米饭吗？
A-not-A: 你要不要吃米饭？ / 你想不想吃米饭？
Choice: 你要吃米饭还是面条？ Answers can be 要/想 or 不要/不想.

Can I drop the subject 我?

Yes, if it’s clear from context. For example, in reply to 你想吃什么？, you can say 要吃米饭 or 想吃米饭. As a standalone statement without context, include 我.

Is 我吃米饭 also correct? What’s the difference?

我吃米饭 is grammatical. Without 要, it states a fact or habit (“I eat rice” / “I’m eating rice”), not desire/plan. For a completed past action, add 了: 我吃了米饭 (I ate rice).

How does 了 (le) change the meaning here?

我要吃米饭了。 New situation/about to start: I’m going to eat (now).
我吃了米饭。 Completed action: I ate rice.
我吃米饭了。 Often implies a change/contrary-to-expectation: I did eat rice (after all).

Where do time and place phrases go with this sentence?

Typical order is Time > (Subject) > Modal (要/想) > Place > Verb > Object.

我今天要在家吃米饭。 I’m going to eat rice at home today. You’ll also hear 我今天在家要吃米饭, which is understandable, but placing 要 before the whole verb phrase (在家吃米饭) is a good default: 我今天要在家吃米饭.

What’s the difference between 米饭, 饭, 米, 大米, and 白饭?

米饭 mǐfàn: cooked rice (Mainland standard).
饭 fàn: “meal” in general; in some contexts it can also mean cooked rice. 吃饭 = have a meal.
米 mǐ: uncooked rice grains.
大米 dàmǐ: (uncooked) rice as a commodity.
白饭 báifàn: “plain white rice,” common in Taiwan/HK; Mainland usually just says 米饭. To contrast types: 糙米饭 (brown rice), 白米饭 (white rice).

How do I specify quantity politely (like “a bowl of rice”)?

Use measure words:

一碗米饭 a bowl of rice (very common in restaurants)
一份米饭 a portion of rice
一点(儿)米饭 a little rice Ordering examples: 请给我一碗米饭。 / 来两碗米饭。

Is 我要吃米饭 polite to say to a waiter?

It’s understandable but a bit odd because you’re stating what you want to do, not what you want to order. More natural:

我要一碗米饭。
请给我一碗米饭。
来一碗米饭。 (colloquial) Adding 请 makes it more polite/formal.

What’s the difference between 吃米饭 and 吃饭?

吃米饭: specifically “eat (cooked) rice.”
吃饭: “have a meal,” not necessarily rice. 我要去吃饭了。 = I’m going to eat (a meal) now.

Can I say 我想跟你一起吃米饭?

Yes. It means “I’d like to eat rice with you.” Word order with more details:

我明天想跟你一起在家吃米饭。 Time (明天) > 想 > companion (跟你) > together (一起) > place (在家) > verb-object.

How do I pronounce it naturally? Any tone tips?

我 wǒ (3rd tone) often realized as a low “half-3” before a non–3rd tone.
要 yào (4th) falling.
吃 chī (1st) high-level; initial ch is retroflex (tongue curled slightly back), not the q sound.
米 mǐ (3rd) often a low “half-3” before 饭.
饭 fàn (4th) falling. Full flow: wǒ yào chī mǐfàn, with wǒ and mǐ kept low then a fall on 要/饭.

Can I say 我不要米饭 to mean “Don’t give me rice”?

Yes. 我不要米饭 = I don’t want rice / Don’t give me rice. For softer preference: 我不想吃米饭 (I don’t feel like eating rice). For a prohibition to someone else: 不要吃米饭。

Is “要不要” a set pattern I can use more broadly?

Yes. 要不要 + Verb/Noun forms a handy yes–no/choice question:

你要不要吃米饭？ Do you want to eat rice?
你要不要米饭？ Do you want (any) rice? Answer with 要/不要 or 想/不想.

Can 我会吃米饭 mean “I will eat rice”?

No. 会 huì mainly marks ability or likelihood. 我会吃米饭 sounds like “I can eat rice” (which is odd). For planned/intentional future, use 要; for predicted future, 会 with appropriate context: 他明天会吃米饭 can mean “He will (likely) eat rice tomorrow,” but desire is better with 想/要.

Do I need 的 anywhere in this sentence?

No. 的 marks possession or turns modifiers into attributives. Since 我 is the subject and 要吃米饭 is the verb phrase, 的 is not used here.