Banks, news media and the mail are full of advice on managing your cash flow. I don't need it. My cash flow trickles in at the rate of a slowly leaking faucet.

What I need is advice on managing my trash flow, which is always at flood stage.

Trashy trash is no problem--empty boil-in-bag bags, nail parings and used tissues. The stress comes from trash that requires decisions. Should I contribute? Join? Sign? Toss? Read? Refer? Burn?

All of it is undisposable (I don't know what to do with it), as opposed to indisposable (I can do without it).

The primary source is the mail, but it also gushes up from newspapers, magazines, pockets, the area around the telephone, and, by spontaneous generation, from any flat surface.

In the absence of professional advice on the subject, I'm happy to share my experience, in the hopes that some may benefit from it.

Let's start with the bulk that comes in the mail six days a week. Discard first--unopened--all envelopes marked in giant red letters "URGENT--Open at Once!" "DO NOT DISCARD" or those with a message showing through the window, "Mrs. Gray, you have already won $2,000,000!!!"

The ones that hide their identity with just a street address have to be opened before discarding, just to be sure. Put these in the stack with bills, the oil-burner contract and requests from Very Worthy Causes, all to be opened later.

Open and read personal letters and put them in a separate pile. (An immediate response is a dirty trick, especially if the writer has owed you a letter for six months or more. The longer you take to answer, however, the higher the chances of losing it and forgetting what it says. Also, if it hangs around too long, the burden on you gets heavier and heavier. Eventually, the statute of limitations runs out and you can forget the whole thing.)

These set-asides join pre-sorted stacks already on the desk, lamp table, coffee table or book shelf--any flat surface near a chair and waste basket. The categories are, roughly: This Week, Next Week, Sometime, Maybe.

There they remain until the heaps begin to slide--by about the fifth day. The categories now start to blur as they fall into each other. Before the bills get irretrievably lost, I cull out the ones I can find, pay a few, and put the less pressing ones back on the stack, which now moves to the dining-room table.

As this mass continues to grow, a fresh stream is flowing in from the mail, joined by unfileable newspaper clippings to keep, deposit slips, notes on books to read, memos on unreturned telephone calls, and, from the pocket of an old sweater, two orange-colored tickets from Fun Services, each imprinted with the command: "Keep This Coupon." Also guarantees for unidentified objects.

When Very Important People are due to arrive, combine all the stacks and resolve to make the necessary decisions immediately.

After opening only the top layer, you will, of course, be overwhelmed. Is a card sufficient for Lou's graduation, or should you send a present? (The invitation is now five weeks old; the occasion is past.) Do you have to read this five-page agreement before signing?

Which do you save--the Seals? The Children? The Sharecroppers? The Democratic Party? The World? Should you buy a set of kitchen knives or an All-Savers Certificate? Join the Y? Get termite control?

The only decision I'm capable of making at this point--The VIPs are almost at the door--is to sweep the whole pile into a cardboard box and move it out of sight (under the desk next to last month's accumulation, to the basement, or in an office, to the janitor's closet behind the mop bucket).

Now the place looks neat for the visitors, and I am relieved that I have handled the problem. Sometimes the boxes remain in "storage" forever, all guilt removed. Sometimes they are activated immediately when, in panic, I tear through everything looking for the auto-insurance bill. The policy is canceled, says the notice, for lack of payment.

The search can take weeks--not because I can't find anything in the boxes, but because I find everything in them.

Here's the proxy ballot from the utility company in which I own stock. I must cast my vote before the shareholders' meeting, which was held four months ago. Instructions on What to Do in Case of Fire. (I must read that. Sometime.) A pamphlet on How to Control Pantry Pests. A subscription blank to a concert series, just ended. Announcement of a course in medieval art, but now they are taking final exams.

Nine letters from Eleanor Smeal, a stack from George McGovern, Tip O'Neill, Teddy Kennedy, Katharine Hepburn, Edward Asner, Norman Lear and Jerry Falwell. Even one from the president of the United States. Announcements of conferences, seminars, weddings, births, deaths. All missed. And newspaper clippings on How to Relax, a travel article on seeing the stately homes of England, a funny piece on the medical treatment of Charles II, and a background story on Rita Lavelle and the EPA. All have to be reread and savored.

There are also money-saving coupons, all out of date, to my relief (I never have them with me at the store anyway). Plus hordes of announcements of management-consulting courses at the U.S. Department of Agriculture, arriving regularly since 1977. I save them to remind me to ask that my name be removed from the mailing list.

The positive side of all this is that time takes care of most of the decisions. Stuff that cried for action on arrival is reduced to a whimper, or muted forever when rediscovered three months later.

In the mad search for the lost bill or the unsigned contract, other things turn up that require a prominent place on the desk or kitchen windowsill. Like the reminder to call the plumber and the schedule for special refuse collection, with letters an inch high proclaiming IMPORTANT across the front, and DO NOT THROW AWAY printed on each page. This is a five-year schedule, which means for the next four years it must be kept in plain sight.

In one of those boxes, maybe under a bed somewhere, is a deed to a cemetery lot purchased by my great-grandmother in 1896. I "filed" it a year or so ago thinking it was worthless, but I couldn't throw it away. Now I have learned it is worth almost $1,000, but I can't find it. What else is at the bottom of those boxes?

If the system described for managing the trash flow doesn't seem functional, there are alternatives: Act on everything immediately or throw it away. Pray for the kind of basement flood I had a few years ago, in which all the boxes collapsed in a soggy mess and were carted away by the Suburban Sanitary Commission. Get a three- or four-tiered desk organizer. (But be warned: They fill up in two weeks, and vibrations from the typewriter will start a landslide, at which time you'll put everything in a cardboard box.) Regularly contribute accumulated cardboard boxes to the special refuse collection.

Or move, and leave no forwarding address.