My technique for fights, is to stay away from them lol. I'm getting to old for that stuff. But here's a sure fire way to get a first lick in(maybe). If someone gets in your face(or better yet, on their way to get in your face, forward momentum will add to the impact), and you know something is going to happen, headbutt the holy hell out of them. If they are taller than you, it will work out great(if shorter, this may not work out great, never headbutt forehead to forehead, it hurts both of you, and that area is harder than hell). Forehead to nose, or jaw will make a good impact. You need to put your whole body into it though. Don't just rear your head back and give them a whack. Step into it. It hurts, trust me lol. It may not drop them, but it "should" give you time to follow up, or get the hell outta dodge. Nothing wrong with living to fight another day!
Disclaimer: Uba Egar is not responsible for said technique causing serious bodily damage, medical bills that may follow, jail time, or an asswhipin that may follow said technique not working out the way the headbutter planed it.