First you have a telephone interview which is resonably easy, you just have to show enthsiasm, willingness to learn and exhibit some technical experience (programming, anything where you had to learn, adapt quickly, disciplines that need skill in logic) Then you have an assessment day, this for me involved one multiple choice test on java, 2 interviews and a day of challeges. The multiple choice test is checking you know basic programming concepts, so brush up on these. The challenges are quite fun and what they are mainly looking for is ability to work under pressure, willingness to put yourself forward, get involved, and work with others. The interviews are the hardest part, good knowledge to bring will be examples of technical achievements, show of commitment to the training/job offer, knowledge of core programming/software development concepts.

Phone interview followed by a team assessment day. The phone interview covers technical knowledge and background. It also covers a specific project you've done in the past, how you tackled it, and what problems you might have faced. The team assessment day includes a technical exam and a group exercise. It is a great opportunity to showcase how you deal and work with others.