The classic WRG approach, similar to that outlined by Norm S, was to classify generals as bold, rash, or cautious, and dice for which class a general fell into the first time it was necessary to know. General’s personalities took effect entirely through the reaction test, with rash or bold generals favouring attacky results and cautious generals being more defencey. The thing I liked about the classification was that there was not a clear ranking of which type was better than any other; while bold was generally the best, rash and cautious both had their different uses. Having simple command modifiers, along the lines of AH’s “Squad Leader”, is all very well, but does not give the leaders any personality to speak of.
I would quite like a scheme based on Kurt von Hammerstein-Equord’s observation that officers could be lazy or energetic, and clever or stupid. He famously used this to establish four categories of officers, of which only the energetic and stupid were useless. Add in a “neither” point on the scale in each of the two dimensions, and you have the possibility of nine different officer personalities, which seems plenty.
What effects officer attributes have obviously depends on the mechanisms in use in the game, so it is impossible to make any specific recommendations without knowing how your intended game works, but I generally think it’s a bit daft to have officer personalities magically making troops move faster or shoot more accurately. Far better have their influcence in the areas of morale and command control, but it depends on having rules that reflect these.
All the best,