No real rule of thumb that I go by.  On shorter patterns the first transition is more likely to be noticeable carrydown.  More noticeable the shorter the pattern.  All patterns will start transitioning toward the middle relatively soon.  I would suggest just the opposite on ball selection.   Use the weakest ball you have that will hook on fresh.  It will give you  a better read of the oil dispersion.  As you get either carry down, or the track starts to force you left, go stronger.  Even tournament patterns have heavier oil in the middle, and further down the lane in the middle. 

Never, never change balls to keep from moving on a lane.  Only exception I have ever seen to that rule is if I am playing 5 board or out, or if I cant get any deeper, and have to go tamer just to keep in the pocket.   

........in my experience most of the time not enough players in the field break the pattern down properly and end up totally trashing it and make it a mess for the rest of transition

+1

I agree with Rico.

I subbed some in a sport league this summer, and bowled a few tournaments and sweepers on sport patterns, and advertised sport patterns.

Of course the first thing I would do is google the pattern to see how it played and gear my equipment for it. I have learned from a  previous incident of being an "advertised" sport pattern that you better bring other sh*t just in case.

I was expecting a flatter oil pattern with out of bounds and tight lines. Ended up with a very unflat and big hooking overall pattern that eliminated 90% of my equipment I brought.

I then learned to keep a full arsenal for any tournament, and have one or two of the 6 balls I take for the specific pattern and the rest for everything else in between. Obviously any of the 6 will work on any possible pattern, but I try to have the two dedicated be the surface/ball/layout I think is best for that condition.(possibly)

I also learned that preconceived ideas of lines are out the window. When you start warm ups, treat it like league or any other event. Pick a good starting ball and go to your A game shot and see what happens. Sometimes you find you can make small adjustments off of your normal line and have a great look. May require a speed adjustment or a different ball, but you are able to play a comfort zone that increases your comfort level.

Also watch others on your pair and around you to see how they are playing the lanes and if they are having better looks in one part of the lane or the other that you may be able to line up off of.

The last thing I learned is do not be afraid to get in and hook the ball. I prefer being on the outside for as long as possible as my A game and moving in deeper as my B to B+ game some days.

I found on more then a few sport patterns this shot is far more forgiving then trying to play more direct on the outside. Standing deeper and having the ball around the 10 board down lane has been a great look. I could have never imagined this with the oil and smaller margins for error when playing further right.

I enjoy getting online to get an idea of what to expect and prep some equipment for. It is when you start bowling on the actual condition and lane that you will gather the most information.

There is no substitute for experience.  Even with experience I am making educated guesses, but at least the emphasis is on educated. 

Yes but left handers generally get trapped in an area created by the right handers migrating in...more times than not too quickly