Japanese speakers
Mistake: Pronouncing every letter as "FA-SUTO TAIMU" with epenthetic vowels and both consonants fully articulated.
Why: Japanese phonotactics disallow the [rst-t] cluster and force vowel insertion.
Fix: Drop the t of "first" entirely — the s links directly to the t of "time": [ˈfɜːrsˈtaɪm]. Native speakers do not perceive the missing t; the pronunciation feels complete.
Korean speakers
Mistake: Preserving the t of "first" with a light release, giving "FEO-SEUT TAIM" with a visible break.
Why: Korean allows complex codas but tends to release them audibly at word boundaries.
Fix: Elide the t of "first" completely: [ˈfɜːrsˈtaɪm]. The [st + t] cluster simplifies to [s + t]. This is the same rule that gives "best friend" and "next day".
Spanish speakers
Mistake: Adding an initial [e] before "first" (Spanish avoids initial sf-... wait, first starts with f, but the r is often trilled), and preserving the t clearly.
Why: Spanish r is a full tap or trill; English r is a light approximant. And Spanish speakers often over-articulate written t.
Fix: English r is [ɹ] (approximant, no tongue tap): [fɜːrst]. Then elide the t before "time": [ˈfɜːrsˈtaɪm]. Trust the reduction.