The best way is to melt the salt and the mustard (if mustard is used) in the vinegar in the spoon (ivory, bone or wood). Then sprinkle the pepper, then the oil. Stir lightly. The proportions are one and a half tablespoonfuls of vinegar to two and a half of oil. Green salads should be eaten the minute they are dressed; you would spoil the best salad by dressing it, say, just before dinner, and even a quarter of an hour makes all the difference in the freshness of the salad and the crispness of the leaves. a vegetable salad should be dressed one hour before serving, so that the dressing has time to penetrate the vegetables.