The way in which you prepare will depend on where you are interviewing. However, in general there are a few broad things you should do:
1. Research the firm. Know about their history, their managing partner, their departments, the type of work they do, what their strategy is etc. It can be surprising how much you can learn about a firm in just a few hours by looking at their grad rec website, their main website, inside buzz (highly recommended) and at articles on the lawyer etc.
Also look into their recruitment process, speak to friends if they have been at a firm, look on inside buzz etc. Know how you are being assessed!
2. Commercial awareness. Keep up with the news in general (not just business news), questions at interviews can be based on almost anything going on so know about the main stories. It us also helpful to look in depth at any stories that interest you, and think about how they could impact the firm/which departments of the firm could work for the possible parties/clients.
I find the best way to do this is watch the news everyday and try to read a broadsheet newspaper every day (I personally find the FT a little too much, remember the interviewers aren't expecting you to be an economist or anything, just to have an interest in business). If you cannot keep up as it is going on, there is nothing wrong in buying the papers each day and in the lead up to the interview read all the papers and look at how stories have developed. Other websites such as BBC news are also helpful.
3. Career motivation. Think, and know in outline how to answer key motivation based questions such as:
- Why did you do/not do a law degree?
- Why do you want to be a solicitor and not a baarrister?
- Why do you want to work in commercial law?
- Why us and not one of our competitors (know how to differentiate firms)?
- If you are interested in business why not be an accountant/banker/etc.
4. Competencies. These parts of interviews are aiming to find out what your skills are and if you can provide evidence for them. Examples include:
- Tell me about a time when you worked in a team.
- Tell me about a time when you lead a group.
- What are your main strengths/weaknesses?
- Tell me about a time where you overcame a challenge and what you learnt about yourself.
To prepare for these, think about your experiences, try to remember any positions of responsibility that you have held, any work experience or employment etc. Think about what skills you demonstrated in each of these roles and the questions above shouldn't be too hard to answer.
Although this is not really a way of preparing, it is important to remember to be yourself. These firms are not looking for robots, try to relax in the interview, answer the questions to the best of your ability and if you have any questions, ask! An interview is a two way process and remember that these firms are not looking to trick you, most are open about what they want in a candidate, so try your best to show them that you process all the skills that make you a solid investment.
My exp: I have secured vac schemes at 4 top firms.