I also took the above exam this week and found it relatively easy. Again it was possibly due to my experience with Microsoft Hyper-V and VMWare vSphere and was able to use my experience to answer many of the question on this Citrix exam. I reckon I could have answered about 20 questions just on this experience alone.
The first step is to take a look at the Exam A26 Preparation Guide found on the Citrix Website
This will give you an indication of what is involved in the Exam e.g 65 questions, pass mark of 64% and 90 mins to complete the exam.
It will also give you links to current documentation that will help with exam preparation such as Citrix eDocs and give you topics that are covered in the exam
I also used the following online courses from TrainSignal.
TrainSignal – Citrix XenServer 6 by Elias Khnaser
Again, this course by itself will not go into the necessary detail to pass the exam so I also used the following book “Citrix XenServer 6.0 Administration Essential Guide” by D Tosatto.
Other useful documents were
Also take a look at the Citrix Blog for other useful information
Don’t forget you can also watch some really good Citrix Videos at