The main thing in planting bulbs to bloom next spring is to get them under the ground and not worry all that much, for I have known people who made themselves anxious with tape measures trying to get a daffodil precisely four inches below ground level.
One year I forgot a few bulbs that were sitting above ground all winter and the poor things bloomed the following April. I planted them and they did all right in later years. Of course they would, since it was a daffodil I do not like much.
It is too elementary to point out, except that when most gardeners see an article about fall planting of bulbs they turn off, so that only the rankest beginner plows on through it, that the pointed end of the daffodil, hyacinth, tulip, allium and so forth points upward. And while it is not critical, the bulb should have about its own height of dirt above it (this is where people get nervous with tape measures) and in general four inches of dirt over the top of any daffodil or tulip will do. So will two inches, though that is too shallow.
Very small daffodils and very small tulips (such as the wild species of both) are safer at two inches, and if they want to they can pull themselves down.
Sometimes you hear astonishing depths recommended, such as a foot deep for daffodils and tulips, and I do not recommend it at all. At such a depth, the plant may never reach the surface. I have personally seen old tulips a foot deep that bloomed for years and years, but I tried it once on a couple of bulbs and feel I slaughtered the innocent.
It is true that the deeper the bulb is planted the more slowly it increases, and this may be a great advantage in that you don't get a lot of small offsets or need to dig them up and separate them. I would say eight inches to the base of the bulb for both tulips and daffodils would work, for bulbs you wish to plant once and then never touch again in this life.
But for ordinary garden purposes it is easier to dig them when they are not so deep, and if you intend to dig them up every three years then the shallower depths suggested will work fine.
A notion that has prevented many from enjoying tulips is that they only last a couple of days and the bulbs are not permanent. This is somewhat true in the deeper South, but in Washington tulips do extremely well, and you will have their glorious color for three or four weeks as a rule, and it seems much longer when you see them every day.
It is a terrible error to cut them for the house, where daffodils last two days and tulips four, while outdoors they last and last. You can grow them specifically for cutting, of course, and cut them with a clear conscience, and they will be cheaper than the ones you buy, and better flowers, too. But in a small garden, it seems wrong to cut the few flowers you have just for a vase. I imagine you can work this out yourself, but I do insist on pointing out that if you leave them alone, in all our lousy spring weather, they will delight you for weeks.
Another thing people are needlessly nervous about is summer dormancy. They think the bulbs should be dry (in general, they should) so they are terrified of planting anything on top of them, once the bulb leaves have died down. In our climate it works perfectly well to plant summer-blooming annuals right on top, clearing them away when they die in November. A great cultivator of the daffodil, and one of the nicest men there ever was, used to grow tomatoes and beans and no telling what else right on top of his daffodils with perfect success year after year.
Daffodils should be planted in September, in my view, though mine will not get in before November this year because of my back. A good bit of the gardener can fall into disrepair, especially the head, without any harm, but the back is important and, as I see, critical, especially if you love to dig. The point is not my grief at my disintegrating bod, but that daffodils may go in as late as Thanksgiving, if they have to (or even Christmas, if you find some you forgot) and tulips are best planted once it gets really cool in November.
One year I had the bright idea to plant California poppies among the daffodils, which would have worked if I'd had a bigger place, but I planted them right on top, expecting the daffodils to rise up like Aphrodite. The poppies did the rising up and the daffodils did not like it.
On the other hand, in really tiny gardens, you can sometimes get away with planting various bulbs on top of one another, not at random, but in certain combinations.
One year I planted the wild Tulipa clusiana about nine inches deep, in a patch three or four feet long and maybe two feet wide, a space shaped somewhat like a fish. I filled in three or four inches of dirt and then planted the wild hoop petticoat daffodil (Narcissus bulbocodium) over the tulips, and filled in another couple inches of dirt and planted a whole layer of crocuses (a mixture of Crocus chrysanthus hybrids, often called snow crocuses).
Naturally, if you plant the bulbs fairly thickly, you may wind up planting the next layer directly over the lower bulbs, and this did worry me a little, but all the bulbs swerved and dodged admirably and made their way up. All of them bloomed, without further attention of any kind, for 12 or 15 years until I moved away. The tulips were contented enough to set seed, and the wild daffodils bloomed steadily year by year, although usually I have trouble with the bulbocodiums after the first couple of years; they send up lots of grass and no flowers. Possibly they thrive on lean diets and heavy competition. I mention this only to show that the gardener, sorely pressed for space in a postage-stamp town garden, can skin a cat more than one way.