I used to heat and clamp and glue--but my advice is that professional adhesive combined with perfect technique eliminates all that.
1.)--remove all traces of old adhesive with a sticker remover pen.
2.) ---research how the flex cables should lie for the device. On the mini almost everyone allows the digitizer flex to fold toward the outside edge. This will cause a screen lift. Instead bend it in toward the LCD, and tuck gently under LCD as in original.
3.) on mini--make sure the LCD shield has no dents--this will cause a lift
4.) apply adhesive stickers ---benji at bowler tech has some great thoughts on adhesives
5.)--fit screen and seal with heat gun and then rubbing of screen edges. Professional. No glue.