ASP.NET : Professional Coding With 3-Tier Architecture

Question

Hi Experts,

I am developing 3 Tier Architecture with Web Service.

Graphically as : (Overall Structure)

                                XML Data                                    XML Data                                   LINQ to SQL Server                          

UI (C# Application) <----------->  BLL (Web Service) <----------->   DAL (C# Application) <------------>  Physical DB  (SQL Server 2008)

My question is that, I need some professional coding tips from you guys.

Right now, System is ready with me.

Sample code would be greatly appreciated.

Note : I am using C#.Net (.Net FW 3.5) and SQL Server 2008.

Thanks.