We have an 8 month old mini schnauzer who is quite a character.

She is a great little companion, the only downside is that when visitors arrive she starts screaming and wailing to get to them, we are expecting our first child in a couple of weeks and don't want a new baby getting woken up by this behaviour.

Can anyone suggest anything to nip it in the bud???? HELLLPPP

while I agree it's best to nip it in the bud ;)   believe it or not your new baby won't be much bothered by it ;)  having already heard it for a few months ;)   

My children both slept thru my friends excited and very noisy Cocker barking right next to their crib ;)  didn't bother them a bit as I never kept the house quiet for baby to sleep ;)  youngest used to wake up if we were too quiet (SCBU baby ;) )

I find the best way to stop my lot being noisy is to do the opposite of what they want until they're quiet  ;)   In your case that would be to wait for her to be calm and quiet before letting her meet and greet.  It isn't a quick fix, but is very effective in the long run ;) a baby gate helps with this as the dog can see but not get to the visitors ;)

There will be more people along soon with other effective ways to cure this :-)

Congrats on the new baby by the way :-D

When I first rescued a Belgian Shepard bitch she was a nutter when people came to the door and in the house. I would ask people to come in and pretend she was not there, sit down and ignore her, I would tell her to lie down or sit then sit down myself I would not let her go up to visitors until she had settled down a bit.
My Mum who didn't trust my girl and [she used to look after her for me sometimes at her house] when people came would over, shut her in the kitchen which had a glass door so she could see all these people and would continually bark her head off, I told my mum that keeping her away was making her more excited/ aggressive in her case! I said once she had had a smell and met everyone she will be OK.
Do not raise your voice when she starts making lots of noise just click your fingers and tell her to sit and give a sweet, people coming in after a while can do this too as she will soon learn being a calm girl will lead to nice treats, she is still young. When I had my son my girl still barked like a mad dog at the door and he would be asleep in his pram oblivious!