Ahhhhh Two year olds - the most stubborn people in the world hehehehe

Seriously though, what works for us is a couple of key things
***Limit the word NO until its REALLY important, otherwise it just loses impact - eg for safety issues or golden rules. We use distraction tactics constantly, 99% of the time they work a treat. You may need to physically pick up your toddler and move them (even to another room) so your distraction is effective though
***I find that DS is his naughtiest on the day I work from home, and the reason why is that he is trying to get my attention while I am working - he doesn't care if its positive or negative attention, he just wants it either way. To address this I find that if I just stop what I am doing, even for 5 mins and engage with him in something he is happy as Larry and will then go on about his business (and I can with mine)
***If a tantrum starts I tell him I'd like him to stop and try my distraction technique, if he continues I either leave the room or turn my back, if there is no audience there is often no tantrum
***Lastly (and I use this to combat DSs 'selective deafness'), get down on hands and kness and in their face when you talk to them or ask them to do something, or put your arms around them so they cant turn away and talk softly, this helps me stay calm as its hard to yell at a toddler when you are practically nose to nose hehehehehe

Ps. Toddler tantrums are completely normal, so don't beat yourself up so much