The promotion process is very fair, and a huge amount of effort goes into ensuring that it is bias free. There are promotion opportunities every six months, which are based on job performance - the option of 'networking' your way to a promotion doesn't really exist.
Training and development are very much embedded in day-to-day life at the firm. A comprehensive review across all the relevant job performance criteria is given for every case, or six weeks of work on a longer project. Informal feedback is also a consistent part of case work, both upwards and downwards.