hit cork first. rest is preference although there is slight flight change between 90degree and e.g. 45degree
In doubles, most coaches will teach you to pinch one of the feathers, and strike the side of the cork in a flick serve, but I personally don't like this method. I find that I have more control of the flight of the shuttle if I grasp the upper cage part of the feathers and hit the tip of the cork flat.
i usually hold it on the tip of the feathers and angled close to 45 deg. not horizontal, it helps me strike the cork with better control and accuracy to where i wanted it to travel
depends whether you do the underhand serve or the backhand serve. backhand you hold it on the feathers, let the cork rest on your strings (its not a foul) and stretch your arms til the racket and shuttle is furthest from you, pull back an inch then swing your racket lightly like you're trying to strike a match. 2 key things here is that your shuttle has to be lower than your ribcage and your racket has to be pointing downwards. underhand, you hold the whole shuttlecock in your palm and drop it, swing and aim for the ceiling
