Terror toddler

Hi guys I'm a dad to a great 21 month old but lately he has started misbehaving a lot, like you say no and he drops on the floor.

I've tried just about everything and I've even given soft smacks (no replys about that please, it's nothing over the top just a tap to let him know) but sometimes nothing's seems to work.

Was wondering if anyone knows some good tips on what to do here, cause when he is being good, he is great, but when he is naughty he is a terror

That's about the time my son started acting up. I send him in his room and tell him he can come back out when he is down with his fit. After a few weeks of that it got better, but i think most toddlers go through something similar.

They will do that to test you, because they are tired or hungry or they need attention/stimulation. Try to redirect him on to something else new and exciting to distract from the bad behavior and if that doesn't work just walk away and ignore it.

Time outs. If redirection doesnt work, give him a time out

Well, if the smacking isn't working, I'd say stop...
Try redirection. If he/she is messing with something they shouldn't be, move it out of the way/reach and give him/her something they can mess with.
Time outs are pretty good too, but sometimes they don't work.
1, 2, 3 method as well. 1 - Warning. 2 - Warn with repercussions. 3 - Act. "Don't stand in the chair.", "If you continue standing in the chair, you'll go to your room for two minutes.", then put him/her in their room.

Thus far, I've had the best experiences with the 1, 2, 3 method.

I love the book how to talk so kids will listen and listen so kids will talk. Any specific examples? I deal with different issues different ways.

The attachment parenting method is really the most effective.
Tantrums are a sign of distress. They are upset and dont know how to handle it.
The quickest way to stop a tanrum is to comfort the child. If he's tantruming when you tell him no, give him a hug and tell him sympathetically that you understand what he wants and you're sorry but that's the way it has to be or you don't want him to get hurt. Then once he's calm, give him something else to do; redirect him as everyone else was saying. But its important that you dont hit and yell. Punishing a child for being upset just shows them that you dont care. Showing them you understand will gain their trust and they will start to listen more.
I have a 20 month old.