In conversation, it’s easy in the midst of spontaneous speech to succumb to verbosity and duplication. In writing, redundancy is less forgivable but fortunately easy to rectify. Watch out for these usual suspects:
Same identical: Same and identical are just that (and that). Omit same as a qualifier for identical.
Since the time when: Since indicates a time in the past; “the time when” is superfluous.
Spell out in detail: To spell out is to provide details, so “in detail” is repetitive.
Still remains: Something that remains is still in place. Still is redundant.
Suddenly exploded: An explosion is an immediate event. It cannot be any more sudden than it is.
Therapeutic treatment: Treatment in the sense of medical care is by nature therapeutic, so the adjective is redundant.
Unexpected surprise: No surprise is expected, so the modifier is extraneous.
Unintended mistake: A mistake is an inadvertently erroneous action. The lack of intention is implicit.
Usual custom: A custom is something routinely and repeatedly done or observed, and usual is redundant.
Written down: Something written has been taken down. Down is superfluous.