Not sure if I'm doing it right but have done several with no problems.
-Clean off old residue. (when no one is looking I use coleman gas and a soft rag)
-If you have spacers to hold window in place (up and down) don't leave out and make sure they are centered.
-I like to use "tackey tape" The name is written inside roll of tape. Much better than regular tape IMO.
http://www.kasonind.com/index.php/products/fabrication_supplies/7513_tacky_tape/Get most anywhere. I like to put on two layers thick. Just mash in place with thumb and peel back paper as you go around frame.
-Screw in screws. Screw in about 1/2 way to 3/4 then screw in a couple thread at a time like your torquing anything else with a bolt pattern, going side to side to pull in evenly.
-In about two months after tape has gotten "mashed out" a bit, take a pop cycle stick and trim. (Maybe best to stock up on pop cycle sticks I tell wife)
-put a very, very thin layer on RTV clear on top of and sides. RTV is just to help water moving. So small that you can't see it when washing or waxing
-Misc notes
-If you have to mess with a very plastic trim known a "window ribbon" a heat gun or hair dryer to make plastic more easy to work with.
-The last window I did was a real challenge. It was a factory "defect" that everybody thought was a leak around the frame, but just factory seam at bottom of butyl had tiny hole at overlap of seam compound. Found
http://www.hehrintl.com/pdf/Hehr%20Service%20Manual.pdf to be helpful after you slug thru and find what your need is.
NOT saying my way is best, just what I've done; your window might be entirely different.
2003 Majestic 23P... Northwest travel machine
2013 Arctic Fox 25W... Wife "doll house" for longer snowbird trips
2001 "The Mighty Dodge"... tow vehicle for "doll house"