Learn Hardcore Japanese: zettai ni tikokusinai you ni, mazu yuugata no densya ni narabu. - To absolutely avoid being late, I’ll first line up for the evening train.

It turns 絶対 (a noun/na-adjective meaning “absolute”) into an adverb meaning “absolutely/without fail.” In careful speech and writing, you normally use 絶対に. In casual speech, people sometimes drop に and say 絶対, but 絶対に is the safe default.

How does 〜ないように work in 遅刻しないように?

A ように B means “B, so that A.” With a negative before ように, it means “so that [something] does not happen” or “to avoid [something].” So 遅刻しないように = “so that (I) don’t be late / to avoid being late.” This pattern is natural with negatives and with potential forms (e.g., 聞こえるように “so (they) can hear”).

Could I use ために instead of ように (i.e., 遅刻しないために)?

ために = a direct, intentional purpose (“in order to”).
ように = a desired outcome or aim, often used when the result isn’t fully controllable, and very natural with negatives/potentials.

Both 遅刻しないために and 遅刻しないように are grammatically possible, but for “to avoid being late,” the set phrase 〜ないように is more common and avoids a possible “because not” reading of 〜ないために in some contexts. Here, 遅刻しないように is the better pick.

Why is 遅刻しない in plain form and not 遅刻しません? How would I make the whole sentence polite?

Subordinate clauses before ように are normally in plain form. The overall sentence is in plain style too. To make the sentence polite, keep the clause plain but change the main verb to 〜ます:

絶対に遅刻しないように、まず夕方の電車に並びます。

Why does 並ぶ take に with 電車 (as in 電車に並ぶ)? Shouldn’t it be を?

並ぶ is intransitive. Common patterns:

Place: 駅で並ぶ (line up at the station)
What line you join: 列に並ぶ (line up in a line)
What you’re lining up for: colloquially 〜に並ぶ, as in 電車に並ぶ “line up for the train.” Using を with 並ぶ is not correct. You could also say 電車を待つ列に並ぶ or ホームで並ぶ.

Does 夕方の電車 mean one specific evening train or evening trains in general? Is this phrasing natural?

It usually means evening trains in general (the trains that run in the evening period). It’s a natural, everyday expression, just like 朝の電車 (morning trains).

Can I drop に in 絶対に and say 絶対遅刻しないように?

Yes, in casual speech people often say 絶対 without に. In writing or careful speech, 絶対に is preferred for clarity and correctness.

What nuance does まず add? How does it differ from まずは or とりあえず?

まず = “first (of all), to begin with,” clearly signaling step 1 in a sequence.
まずは = slightly softer or more conversational; similar meaning.
とりあえず = “for now/for the time being”; can imply a temporary or stopgap action rather than an orderly step.

Who is the subject here? Is it “I,” “you,” or “we”?

Japanese often omits the subject. Context decides:

Planning/diary voice: “I’ll first line up …”
Instructional/advice context: “(You) first line up …”
Group plan: “We’ll first line up …”

Is the comma after ように necessary? And what about the spaces in the sentence?

The comma 、 after ように isn’t grammatically required but is common to mark the clause boundary and improve readability.
Standard Japanese doesn’t use spaces between words. The spaces here are just for learners to see the word boundaries. Normally you’d write: 絶対に遅刻しないように、まず夕方の電車に並ぶ。

What’s the difference between 遅れる and 遅刻する? Could I say 遅れないように instead?

遅れる = to be late/delayed in a general sense (a person, a train, a schedule).
遅刻する = to be late to a formal obligation like work or class. If the context is work/school, 遅刻しないように is more precise. 遅れないように is broader and fine if you just mean “not be late” generally.

How does 絶対に compare with 必ず? Can I say 必ず遅刻しない?

絶対に = “absolutely,” strongly emphatic; works naturally with negatives: 絶対に遅刻しない (“absolutely won’t be late”).
必ず = “certainly/without fail,” typically used with positive statements: 必ず行く (“I will certainly go”). Avoid 必ず〜ない; it sounds odd or can be misread. Use 絶対に〜ない for “never/absolutely not.”

What’s the difference between 〜ように and 〜ようにする? Could I say 絶対に遅刻しないようにする?

〜ように: sets up a purpose/aim clause for the following action.
〜ようにする: “make an effort to/ensure that ~.” So 絶対に遅刻しないようにする = “I will make sure not to be late (I’ll take measures).” In your sentence, 〜ように、まず…並ぶ presents one such measure.

Are there more explicit or alternative ways to say “line up for the train”?

Yes:

電車を待つ列に並ぶ (line up in the queue for the train)
ホームで並ぶ (line up on the platform)
電車に乗るために並ぶ (line up in order to board the train)

These are all natural; the original 電車に並ぶ is also fine in everyday speech.