First, welcome!
Not sure if these are the steps you are looking for but setting up an attack can take some time from initial contact is made. Surprise contacts at close range are another matter and for that I would give it a miss most of the time.
For normal attacks I would
1) Contact be it visual or sound: Plot the best you can target course and speed. Keep your distance to allow yourself to travel on the surface to overtake and reach attack position. Dive when approaching position or some time before distance to target is getting small for them to detect you.
2a) If you are confident your plot is good in respect to target course and speed, and visual confirms it, you can set up for a 90*short to medium range straight shot where distance to target is less important but you will still need a good approximation of target speed and course.
2b) If you believe your plot is too inaccurate for a 90* straight shot solution, you have some options like
http://www.subsim.com/radioroom/showthread.php?t=222377
EDIT: On that last point, 2b, I can personally vouch for at least the 2nd method works well for non standard shots. One successful attack I made using the 2nd method had the target getting hit when it was at my 320 to 330 bearing, AoB somewhere between 75 and 85, distance about 2000 meters.