I can't think of 2 off the top of my head.
firstly, "Metering in Manual" as a fellow Tog told me one day.
I was shooting festival downtown, and found myself next to a very knowledgeable local Photographer. We talked about his 5D mark II for a minute or two, and the benefits of possibly upgrading to the Mark III..... went off shooting for awhile, then when we bumped into each other again, he said something along the lines of; "By the way, a quick tip: try metering off the band members faces. With such shadows on the band, and direct mid-day sunlight on the background, it's challenging to get the exposure right. I've found that Metering in Manual is the best way...."
I didn't realize you could meter in Manual before that. I thought that was a AV/TV function. So when I got home, I Googled manual metering, and found that the little line in the viewfinder at the bottom, with the tic marks and numbers was the meter! -Hot Diggity! I immediately got quicker at getting proper exposures.
the other was, when I was starting out, I felt like it was cheating to use any sort of Auto mode. so for the first few months of shooting, that dial stayed on M. no Autofocus either. (though the lens I was using did have a bit of a hunting issue....or perhaps that was operator error.... in fact, I'm pretty sure it was)
After shooting for awhile, I started trying to teach myself how to use all the tools available. AV/TV, Autofocus and the various methods, metering, exposure comp.....
and then it dawned on me. A pro will use all the tools available to him. and won't excuse Priority modes as cheating.
I wouldn't change how I learned. I feel I have a decent understanding of all the things going into a proper exposure. but now I can get the same results in a much much faster fashion.
Sorry, I find myself a little long winded sometimes....
-RW