United States: refused under 214(b)
A 214(b) refusal means the officer was not convinced you would return home; it is not a finding against your documents. Your DS-160 and the officer’s notes from the first interview stay on the system, and the next officer reads them before you reach the window. A second interview with the same answers is the same interview. What changes a decision: a stronger reason to return (a job offer, a business, property, family responsibility), a clearer funding story with exact numbers, and answers that are specific where the first ones were vague. There is no waiting period; you pay the fee and book again.
United Kingdom: a refusal letter with reasons
UK refusals come in writing with the paragraph of the rules you failed on, so you know exactly what to fix: usually credibility (the course did not fit your history), funds (the money was not held for the required period) or an unexplained gap. For Student visas there is no appeal, only a fresh application, and the credibility interview, if there is one, will return to the same points. Fix the point named in the letter, then prepare the interview around it.
Canada: the GCMS notes
Canada rarely interviews, but a study-permit refusal letter is short; the detailed reasons are in the officer’s GCMS notes, which you can request. They tell you whether the problem was purpose of study, finances or ties. A new application should answer the notes directly in the study plan and the explanation letter.
Schengen posts: the refusal form
A Schengen refusal gives one of nine numbered reasons on a standard form: most often "the information submitted regarding the justification for the purpose and conditions of the intended stay was not reliable" or "your intention to leave the territory could not be ascertained". The reason tells you which part of the file was weak. Many Schengen posts offer a remonstration or appeal within a short window; otherwise reapply with the weakness fixed.