If you install Visual Studio 2010 SP1 and then you find that IIS will not start, you may have a port conflict issue.  SP1 includes a new service, the Web Deployment Agent Service.  This new service runs on port 80, the same default port that IIS uses for HTTP traffic.  If the Web Deployment Agent Service is running, IIS will not start if you are using port 80 in IIS.  On option is to modify the web deployment agent service.  For me, I stopped and disabled since I do not plan to use.  You may be able to change the port is uses by default.  Additional info can be found at the link below

http://superuser.com/questions/282519/change-the-port-of-iis-7-5-express

If you want to debug a WCF service you may encounter the following error in Visual Studio:

IIS specified authentication schemes 'IntegratedWindowsAuthentication, Anonymous', but the binding only supports specification of exactly one authentication scheme. Valid authentication schemes are Digest, Negotiate, NTLM, Basic, or Anonymous. Change the IIS settings so that only a single authentication scheme is used.. ---> System.InvalidOperationException: IIS specified authentication schemes 'IntegratedWindowsAuthentication, Anonymous', but the binding only supports specification of exactly one authentication scheme. Valid authentication schemes are Digest, Negotiate, NTLM, Basic, or Anonymous. Change the IIS settings so that only a single authentication scheme is used

This can occur if the virtual directory hosting the service in IIS has both the Intergrated Windows Authentication and Anonymous authentication schemes selected.  In order to get around this so that you can debug your service, you can do the following:

1. In IIS, uncheck the Annonymous scheme
2. In IIS, leave Integrated Windows Authentication checked - this is required to run the VS Debugger
3. Start the debugger from VS
4. Before you make a request to your service, go back into IIS and check the Annonymous scheme
5. Make a request to your service and your break point will be hit
   

The infomous Object reference not set to an instance of an object error occurs when you try to reference or use an object that has not been set to a valid "value" or instance.  For example, let's assume you have a Class "Person" that has a property Name.  If you try to access the Name property and your Person object is not set to an instance, you will receive the Object reference not set to an instance of an object error.

In code:

Person p = null;
p.Name = "John Doe";

This is an obvious case, but what makes this error difficult to track down at times is when you do not know why you do not have an instance of the object.  This can occur for a variety of reasons.  If you are able to create a unit test (or already have one) this can help you to track down the root cause.  You can also rely on the stack trace and/or debug the offending code.

A while back I passed the Oracle Certified Programmer for the Java 2 Platform SE 6.0 (formerly SCJP 6) exam and thought that overall it was a challenging exam.  The questions required you to have a good handle on the language and framework but you really needed to concentrate on each question and look for small details that would result in the correct answer.  

As for content, if you follow the SCJP Sun Certified Programmer for Java 6 Study Guide by Katherine Sierra and Bert Bates book that will give you a good start on the content.  I also recommend a mock test, such as the one offered by whizlabs.  I used this and found it to be helpful to familiarize myself with the exam format.  Javaranch is also a good resource.

SCJP 6 Exam Simulator http://www.whizlabs.com/

http://www.javaranch.com/

Good luck!

I recently passed exam 70-523 to earn my MCPD .NET Framework 4 certification.  The exam covers a fairly wide range of topics and the following provides an overview of the sections to expect on the exam.

There are 5 seperate tests that you will take during the exam and this includes one real world scenario statement follwed by 6 questions on the requirement statement.

The tests break down into the following:

1. WCF with .NET 4 - approximately 20 questions
2. Web Application development with .NET Framework 4 - approximately 20 - 30 questions including topics on MVC and Web Forms
3. Accessing Data with Microsoft .NET framework 4 - approximately 20 questions including topics on EF, LINQ, and DataTables
4. Designing and Developing Web apps - 20 questions + the real world scenario statement & quesitons

The exam was moderatly difficult but if you have about 1 years experience in .NET 4 including MVC, EF, LINQ, and WCF, and jQuery you should do OK and no need to get a vce or brain dump or anything like that.

Some additional resources I found helpful:

http://gregorsuttie.wordpress.com/2011/01/01/net-upgrade-exam-70-523/

http://www.microsoft.com/learning/en/us/exam.aspx?ID=70-523#tab2

 Good luck!