Do your research on the company, and if you can then engage with someone prior to interview who already works at the company.
For an internship interview, prepare a few different examples that highlight your strengths and growth areas. For the graduate assessment during an interview, work hard and ask as many questions to as many people as possible.
Get the highest grades possible. Understand the commercial reality of the industry. The company does not just want the best technical graduates. Instead, they hire graduates that understand that the company works in a competitive market environment with real environmental/political influences.
Be yourself. Read up about the company culture. Often that can be the clincher between a candidate that makes it or doesn't.
Start following and understanding industry related news, trends, and developments. Focus on more than academic achievement if you are already strong in this category, otherwise, make sure they are up to scratch. Get involved in activities outside of university where you have a chance to develop your own communication and leadership skills - particularly in situations requiring a high level of creative thinking.
The usual: talk to people from the company, get to know the company values and culture; learn the assessment criteria and build the company jargon/language into your examples. Don't be afraid to attribute success to yourself rather than a team. Ability to work in a team will be evident from your group achievements but really concentrate on what 'YOU' contributed and why that added value.
Be yourself, it's alright to be nervous everyone is, enjoy the experience
Practice psychometric testing, prepare responses to generic graduate recruitment questions. Prepare examples from experiences for generic scenarios.
Read through whatever information you can find on Shell Recruitment Day and be confident on that day itself. Bear in mind that interviewers are there to give points/reasons to hire you rather than points/reasons not to hire you.
Research the company, their culture and their projects
Be yourself, try to embrace as much life experience as possible before applying for the role. It doesn't matter what knowledge you have of the industry, what is most important is coming in with the right mindset, openness to diversity and willingness to learn.
Be confident and be willing to talk about an issue for a while. Know what Shell wants in a person.