If it's one on one, i'd take him down and play around with him. Though that depends on how I feel. If I'm angry I might just wanna finish it fast. And I'd do that standing up. If there are several of em, standing up is obviously the best and only way to go. Not only because if you're on the ground they might kick you bla bla bla. But because you'll finish them off 10 times faster standing up. And that's what you need to do if you fight several people at once.
Say there are four or five of them. The first guy is a goner right away. Simple light flick with the jab sort of to distract him and instantly your right hook hits him on the chin. The first guy is the easiest. Most of the time, the rest of them wouldn't want to fight you after that. But if it happens anyway, they won't go at you all at the same time. Doesn't work that way. So when the next guy comes, punch him in the face, or kick him in the balls. Whatever you can to get him out of the fight. Wether temporarily or permanent doesn't really matter at that moment, because there are more guys to deal with. Depending on how the guys react to that (do they want to fight? are the aggressive/passive? steroid "i-wanna-die" type people?) you either stay passive and see what happens. See what they say. If you can you should leave.
If you're not confident you'll knock em both out, run away. Because if they get you and you've just manhandled two of them, they might go as far as to kill you if you're unlucky.
But EVERYTHING depends on the situation. How many they are. What KINDS of people they are. There is so much to take into consideration. There isn't really a book you can read that tells you, "this is what you do when you get into a street fight". Because 99% of the situations are unlike any previous situations you've been in. So you kinda have to "take it as it comes".
The last time I got into a "scuffle" was at a party. I went by to say hi to a couple of friends I hadn't seen in a long time. I got like two beers in me before one of them wanted to "fight" me. He knew I was a fighter and well... for some reason people always want to test you/themselves). Especially when they've been drinking.
So we were outside. On the lawn and not on pavement. I got into the clinch right away. Took him down and ended up in his "open guard". I decided to be nice so I went for the achilles hold and cranked it as hard as I could. It hurts but it won't break his leg/arm or something like that. So I was being nice. He screamed and I put some more strength into it for like 2-3 seconds and then I let go, stood up and that was that. He limped back inside.
Then another guy back inside who heard about what happend wanted to try his luck. This guy was bigger than the first guy. I got into the clinch, and he gave alot of resistance so I went for the legs. I got him down and got the mount right away. I started slapping him in the face and he covered up. I grabbed one of his arms and went for the armbar and cranked it. Although not as hard as I could or anything. I didn' t really want to hurt him because I had my friends there and there were girls there watching and the party would've probably ended or something. But I cranked it hard enough for him to feel it and he started to moan and gave up.
The party continued and everyone was happy. End of story.