My DS started throwing MAJOR tanties at 12months as well. If i had to tell him no (which was a lot of the time because he would always want to play with anything dangerous!) he would absolutely loose it. It got so bad that i seriously considered staying home from mum's group and avoiding taking him to other peoples houses because i knew as soon as i had to stop him doing something or he wanted something he couldn't have he would explode (and i mean really EXPLODE! he could stop crowds with his screaming!) I tried distraction but that only worked sometimes, most of the time the only thing that would work was to take him away from whatever he wanted ( of course i'd explain why i was taking him away and why he couldn't have it but half the time he couldn't hear me anyway because he was screaming so loud) and sadly a lot of the time that meant leaving friends houses, or any social scene (not that i got out much) At the time this was really hard, especially when i'd go to mum's group and all the other bubs were angels and then there was my DS screaming in the corner because he wanted sometjing he couldn't have. He's also very inquisitive and has always had a thing for trying to figure out how things work so if he's into something that is relatively safe to play with i just let him go. At the time i would just keep reminding myself that its a good thing that he's so inquisitive and 'out spoken' ( but i tell ya some days were very hard especially after what felt like a whole day of tanties) I think a lot of the problem was he was so young and couldn't tell me what he wanted so he'd scream out of frustration.
He's now 2 years old and its taken A WHOLE YEAR but he's now so much more mellow and i can tell him no without a tantrum which is heaven
Its funny because now the other bubs at my mums group are starting to throw tanties now whereas my little boy has settled down. I'm thinking maybe my DS just started the 'terrible twos' early (fingers crossed it wasn't just the beginning!)
Anyway i guess i can't give you much advice other than to just try and find a positive in the situation- loud now eguals strong willed and determined in adulthood Stay firm yet loving, consistent, and find some time to destress!