Howdy Carl, welcome aboard.
Yep, its an ongoing problem.... Sometimes you turn the bowl and sometimes the bowl turns you
Here is a short list of things I've found to help:
Agree with all of the above...
Consistent wall thickness, uneven walls (thicker bottoms) cause uneven stress and make it more likely to crack on the thinner parts. If I'm doing twice turned bowls (rough green, dry, return) the general rule of thumb is 1" of wall per 10" of diameter, although I've had mixed luck there as some bowls tend warp more than others so returning can be a trick. If turned to finish, then it depends on how dry the wood was originally. If it was pretty dry then you can get away with more variation, but if its wet then .. its trickier... the bigger the bowl blank the less likely it is to have an even moisture content.
Differential drying. If the inside of the bowl dries faster than the outside it puts the wood in compression, if the outside dries faster it puts the wood in tension which tends to pull it apart. Wood in compression is quite strong and less likely to crack. There are a lot of ways to do this, you can wrap the outside with plastic or paper, pack the bowl in shavings (leaving the center open and taking out to "air" every few days to avoid mold), and .. others. A rather dramatic example I had of this was a fairly large (17") calabash bowl I was finishing I slathered the inside with a water born poly and it started making some horrid cracking noises, realizing what I had done wrong I immediately soaked the outside with the poly and and the movement stopped.
For weird grain or other risky looking bits (pith spots, etc..) I'll sometimes saturate the area with glue (CA or white glue usually... play around with what works with your finishing routine). One larger bowls I'm planning to re-turn I'll hit the parts that are end grain with white glue and plan on just turning it away once its dry enough.
I haven't played with most of these much but there are lots of other drying methods. You can soak the bowls in a large tub of denatured alcohol (1 day per inch of thickness) which changes the drying mechanism somehow. You can use stabilizers like PEG. Boiling wood also stabilizes it (rough turn, boil 1 hour per inch of wall thickness). On turner from Hawaii soaks his work in a specific type of liquid dish soap which also acts as a lubricant when he re-turns them (he does mostly "see through" super thin stuff), and... the list continues.
As you've probably gathered by now this is an ongoing problem so you are certainly not alone
The solutions are a varied as the turners and the wood (this is pretty common, ask three turners about something and you'll get six opinions).