We are beating this to death, but I too started on a Dillon 550B [dada dum
]. I haven't made any life threatening mistakes and I am getting pretty darn good at it now. I also had my dad to check in with since it is at his house and I ran by all of my reloading tales with him and he advised me. Other than that, I have been doing pretty good with it. Like everyone says, you just have to pay attention to what you are doing. Get in a good habit of doing all of the steps in a specific order and stay with that order. For me, I will not leave the bench unless I pull down the handle, rotate the shell plate and then put a new bullet into the cartridge waiting to be seated. When I come back, I know I just need to start from the begining again. Just things like that will keep you from double charging (if it is possible, depends on the load you are doing) and blowing yourself up. Good luck.