Lots of packages must travel across the miles at Christmas gift's lovingly chosen, fancily wrapped, and carrying as well a precious burden of affection for someone. Yet millions of these packages travel at a time of year when the post office facilities are extremely overtaxed, help is often inadequately trained, and weather conditions are, in general, poor. How can we be sure our packages will get there on time, and in good condition?

Start with a packing plan. Make a list of the packing supplies that you'll need string, tape, labels, cartons and buy them all in one trip to the stationery store.

The very best container for a Christmas gift that must be mailed is a fresh new cardboard carton. Sometimes you can obtain from local merchants cartons which are in excellent condition, with firm corners and intact flaps. Or they can be bought; buying a carton is well worth while if it protects a valuable present.

If there is even a remote chance that a gift could be broken or crushed, use two cartons, one inside the other. The inner carton should be big enough to allow at least a 2 inch clearance all around the package enclosed on all four sides as well as at the top and bottom.

Don't let a present rattle around in a carton, whether you use two, as recommended, or one. The best, cheapest cushioning is shredded newspaper; crumpled newspaper doesn't have enough give to protect the gift from the shock of handling. Use enough shredded paper so that there is no rattling or shifting when the package is shaken back and forth.

For the utmost safety, make out two labels: one for the outside and one to be placed inside the carton. The post office objects to more than one label on the outside, but if you express the package, use two outside labels.

Use the full names and addresses of yourself and the recipient of the package; don't use abbreviations. And even if you feel you write a good hand it is always better to print than to use handwriting.

Tie up your carton with medium-heavy cord, wound tightly around the entire package at least two or three times and knotted with simple double knots. Very heavy twine is not as safe, strangely enough, because it is too heavy to pull tight and therefore slips off the package more easily.

Regulations governing packages to be mailed within 150 miles are different from those for packages to be mailed farther than that, as far as the weight permitted is concerned. There is another regulation for the weight of packages which have an APO address. Check these rules with the post office if you want to send heavy packages, since the rules may change from time to time. You may express a package of any weight, no matter how heavy.

The post office strongly advises December 1 as the deadline on mailed packages. It's better to chance their arriving a bit early, with a DO NOT OPEN UNTIL CHRISTMAS sticker, than to run the slightest risk of their not arriving until the day after The Day.

Expressing by rail or air are quicker methods, of course, than mailing a package; be sure to investigate these ways if you've let an important package slip past December 1.

Flat, non-breakable objects, such as books, need a double corrugated-paper covering. Envelop the book lengthwise in a corrugated strip, seal with gummed tape. Wrap a second strip around the width and seal. Use heavy brown paper for outer wrapping.

If you are sending a very small package in a box of its own, you must enclose it in a larger carton to be sure of its safe delivery, and cut down the danger of loss.

When you follow these guidelines, you can be sure you gift will arrive on time and intact.