An easier way to remember is that unveil requires that something is first of all covered by a veil or a cloth. Then the veil or cloth is removed. To reveal simply means to show something that was hidden.

unveil is usually what you do to an object/information (the truth has been unveiled) what I found from www.thefreedictionary.com : Verb 1. unveil - remove the veil fromunveil - remove the veil from; "Women must not unveil themselves in public in Islamic societies" uncover, expose - remove all or part of one's clothes to show one's body; "uncover your belly"; "The man exposed himself in the subway" veil - to obscure, or conceal with or as if with a veil; "women in Afghanistan veil their faces" ***2. unveil - make visible; "Summer brings out bright clothes"; "He brings out the best in her" bring out, reveal, uncover show - make visible or noticeable; "She showed her talent for cooking"; "Show me your etchings, please" disclose, expose - disclose to view as by removing a cover; "The curtain rose to disclose a stunning set" excavate, unearth - recover through digging; "Schliemann excavated Troy"; "excavate gold" trot out - bring out and show for inspection and admiration; "His novel trots out a rich heiress"; "always able to trot out some new excuse" unfold - open to the view; "A walk through town will unfold many interesting buildings" 3. unveil - remove the cover fromunveil - remove the cover from; "unveil a painting" while for revealed: 1. a. To make known (something concealed or secret): revealed a confidence. (disclose/divulge a secret) b. To bring to view; show. 2. To make known by supernatural or divine means unveil contains an additional physical meaning to it, which includes the physical action of actually "withdrawing the covers" from something previously not known, and can be used figuratively to refer to that action of presenting new, previously unknown information/objects while reveal contains all of that, minus the direct association to that physical action. reveal is also used biblically.