Now that the height of the lecturns and other weighty issues have been decided, George Bush and Michael Dukakis are setting themselves to the next task at hand: Sunday night's big debate.

Both have been reviewing some facts and figures - what the Contras and defense and education are costing us, and the like. Also, the candidates have been spending much of their preparation time on strategy: How to appear presidential. Whether to be folksy. How to answer the old questions in reassuring ways.Just as the candidates have been girding themselves for the televised confrontation, the electorate ought to make some serious debate preparations of its own.

First, decide what really matters. How important is packaging? Do the clothes - or shave - make the man? Would a bad case of nerves during a nationally broadcast debate return to play a role in next year's international crisis? Try to answer these questions for yourself before you tune in.

More important, how will you know if either candidate has a grasp of his subject if you have no grasp yourself? You can read about the gaffes in the next day's paper, but understanding of national and world events takes a little longer to acquire. Do you read the tall headlines and skip the print beneath them?

Even if you're well-read, you may not be sure of your own opinions. Sometimes people don't really know what they think until they try to express it. When did you last express your political philosophy to a family member or a friend? Or in a letter to the editor? If you don't know what you think and why, you may be vulnerable to a candidate with clever phrasing but little to back it up.

Dukakis and Bush are ready for their debate Sunday evening. Are you?