LINQ to SQL Web Application Best Practices

In my experience building web applications, I’ve always used a n-tier approach. A DAL that gets data from the db and populates the objects, and BLL that gets objects from the DAL and performs any business logic required on them, and the website that gets it’s display data from the BLL.
I’ve recently started learning LINQ, and most of the examples show the queries occurring right from the Web Application code-behinds(it’s possible that I’ve only seen overly simplified examples). In the n-tier architectures, this was always seen as a big no-no.
I’m a bit unsure of how to architect a new Web Application. I’ve been using the Server Explorer and dbml designer in VS2008 to create the dbml and object relationships. It seems a little unclear to me if the dbml would be considered the DAL layer, if the website should call methods within a BLL, which then would do the LINQ queries, etc.
What are some general architecture best practices, or approaches to creating a Web Application solution using LINQ to SQL?

Implement a Save method for my object

I’m trying to improve my application’s design, So instead of calling the DataAccess layer from the presentation layer. I’ll try to implement a save method from my object in the BusinessObjects layer. but I’m not sure how to pass the object or it’s properties through the layers. for example in my old design I just create an instance of my object in the presentation layer and assign it’s properties then just call the DataAccess method for saving this info in the database and pass the object as a parameter as illustrated.