Ermm well I've always been a saver rather than a spender, so I had saved vast amounts through birthdays and the like already... then I worked 20 hours a week during upper sixth (I was a year ahead - so not old enough to work in lower sixth properly) and then really worked loads in the holidays. Then last summer I worked so so much in bars I almost killed myself.
But, to be honest, the main trick as to how I do it involves my bar management position. Although it was voluntary: after term 1 of uni I hardly paid for a drink (Except when I went out afterward, but I would ensure I was already at a suitable level and just had to keep topping myself up with drinks on a rare basis), that's nearly 2 whole years of no drinks bought out my own pocket and I still spent all my loan! Living off just a loan must be tough.