Help needed, how do you publish a webapp?

as probably happened to many of you, some time ago I've got an idea for a webapp I would have liked to build.

Months have passed and it is almost ready, I would publish it on the internet.

I don't think it'll get me rich, but it would be nice to see how good or bad it performs and if mine was actually a good idea or not.

I worked on it on my own and I'm looking for a nice and cheap hosting company.

But now what I'd like to ask you is the following: which are the steps you think I should take to get the most out of this experience?

What would you suggest me to do or not to do? What did you do wrong? Who would you contact for funding, testing or market it?

I live in Italy and we don't get many networking events here, but I'd be definitively available to spend some money if it's worth it.

Thanks in advance for any hint you'll want to provide.

--- update ---

Actually, my very first mistake was not to notice this: http://ycombinator.com/lib.html

now I have and I'm going through some of the links, they're great.

Still, I'm open to any hint you may also have.