To the OP, Premed can only be used once, in stealth.
So if you want to use it, use it before your opener ... then follow with your normal shot rotation. If you hit 5 CP's, use KS, if not, continue with your combo builder until you do have 5 pts, then use KS.
It's really quite as simple as that.
This was answered in the very first reply, and the reason it's not covered in the sticky, is because all the information you need is in the skill's tooltip, so I'm not sure why you persevered with the question ... unless, of course, you're trolling.
As for asking what spec is the quickest to level, then getting stroppy when you're told to read the stickies (where the answer to that question appears in more than one place), that's just opening yourself to the flaming you got.