Logging in Sharepoint 2010

Logging in SharePoint 2010 is a pretty straight forward affair. The code block below will write to 14\LOGS 

using Microsoft.SharePoint.Administration;

                SPDiagnosticsService.Local.WriteTrace(0,
                    new SPDiagnosticsCategory("CustomComponent", TraceSeverity.Unexpected, EventSeverity.Error), TraceSeverity.Unexpected, ex.Message, ex.StackTrace);

If you want to create your own custom logging component, the following two blogs will assist you.

http://blog.mastykarz.nl/logging-uls-sharepoint-2010/
http://www.sharepointproconnections.com/article/sharepoint-development/SharePoint-Logging-What-s-New-in-SharePoint-2010.aspx