We have Zorro who is coming up to 5 months and definitely has his Dennis the Menace couple of hours each day (thankfully Bella takes the brunt of it for us, she is a patient little soul!

). But we have noticed that he is far worse when he has been overstimulated, eg has had a new and exciting experience or is just over tired - he will then not settle down at all and goes on all evening. If he's being too much we stick him in the kitchen with a chew but other than that, once we've played with him or done a bit of training, if he still harrasses us he gets ignored as he needs to learn to settle down.
Bella was just full-on all the time, hanging off our trouserlegs, loads of mouthing and always wanting to be busy, I'm trying to remember what we did with her but I think it was just lots of playing and training - esp training as it used to tire her out with all the brainpower involved (she really, really concentrates!).
I think playpens are great, we used one for both of ours when there were a bit younger and it helped a lot. Zorro's a bit big to go in one now so he gets put in the kitchen with a chew or kong if he's being too much.
So basically I think you need to do little playing sessions, training sessions and get a playpen and put him in there with a nice chew to keep him busy, and really praise him for lying down chewing something he's supposed to.
Also with the reprimanding, we've found with both ours that shouting just excites them more, they respond much more to a stony look and a low, grumbly, very firm "Nooooo". Zorro is a fiend for jumping up at the moment (on us, on the sofas, you name it) so he gets told "Nooooo" and then "Floor" (which means all 4 feet on the floor) and then praised as soon as he does what we've asked. Also try anticipating his moves, so if he's about to go and chew something he shouldn't, do a sharp "AH-Ah" and quickly give him something he IS allowed to chew.
Other than that, you just have to ride it out I'm afraid...
