PREPARE, IF you will, for Congress at its collective craftiest -- which is that time every year when the members seek the quietest new ways possible to maximize their incomes and minimize public reaction. The idea of this game is to avoid at all costs -- well, almost all costs -- anything resembling a roll call vote on a direct salary increase, because that is bound to sit poorly with beleaguered taxpayers whose incomes don't even approach the congressional figures. Instead, you look for well-camouflaged proposals to augment salaries; and if you look right now, there are a few floating around the Capitol.

As reported by Capitol Hill reporter Richard L. Lyons, the current focus is on what limits should be placed or kept on earned outside income (not dividends or inherited wealth, but speeches and other work). There is nothing inherently wrong with either of these appraoches, nor should some increase in the allowable incomes of members be automatically out of the question. Even though the present congressional salary of $60,662.50 is no small potatoes to most constituents around the country, dual residences and other expenses can eat into this income.

In the Senate, where the effective date of a 15-percent-of-salary limit on earned outside income has been postponed, members still are forbiden by law to accept more than $25,000 a year for speeches. In the House, Rules Committee chairman Richard Bolling (D-Mo.) says he has been under "considerable pressure" by some members of both parties to report out a rules change rasing the 15 percent limit. He adds that he favors some increase and will hold hearings.

Most important, Rep. Bolling says that whatever is done should be done deliberately and in the open. That, of course, would be a ghastly break with revered custom. But in a year when there are no lame ducks in season, it may be futile to wait until the last night in Legilative '81 to slip in pocket-liner provisions. If there's a case for easing the restrictions -- and even Common Cause thinks once can be made -- it should be presented and considered openly. That's not too much to ask, when you consider who's paying the salaries.