Beata / Betty,
In my experience, the assessment centre was relatively painless and involved the following:
1. Group exercise - within the group, work your way through a case study (incl. printed materials). The exercise requires you to approach the ‘client’ (i.e. the assessors) in character in order to delve deeper into their backgrounds. Note that some of the clients will have experienced similar problems in their previous companies. Finally, you must present your conclusions to the ‘board’ and answer any questions. My advice here would be to share tasks evenly and state your focus early on – e.g. one team looks at reducing costs while another looks at increasing revenue.
2. In depth case study - you'll be given a pack of information and approximately 40mins alone at a computer to prepare a summary slideshow. You then present this to a 'colleague' (i.e. the assessor). This exercise mimics a 'blue review' meeting, in which one team briefs another on the nature of their project and invites their insight. So, the name of the game here is to paint a complete picture without getting toooo bogged-down in detail/numbers. Keep it snappy!
3. Creative exercise - e.g. “If you wanted to run for Mayor next year, what would you do?” You’ll have 3 minutes for thinking, 3 minutes for preparing and 3 minutes to present.
4. Written exercise - e.g. “Draft an email to the manager of your Client's organisation to express your disappointment in his/her team's commitment.” This was surprisingly challenging to do diplomatically!
Anyway, I hope this helps and that the format hasn’t changed too much! All in all, I found it to be quite an enjoyable and relaxed day.