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...What kind of stand and how high should I use it? Should the speedlight be angled down at 45°?
The height of the stand depends on the flash-to-subject distance: the further away, the higher it needs to be to keep the same angle.
What that angle should be depends on several factors, including the subject's features (deep-set eyes or shallow?), clothing (wide-brimmed hat?), pose (looking up at the camera or down at a ring or bouquet?), etc.
In addition to Neil van Niekerk's site mentioned above, also check out his books:
The first one is especially good for those just starting out.