Foods You CAN Eat with Your Fingers
Artichoke
The artichoke is actually the leaf-enclosed flower bud of a plant that is in the thistle family. It is usually served steamed with a dipping sauce. To eat it, pull a leaf off, dip it, scrape the flesh from the base of the leaf with your top teeth, and discard the leaf on the plate provided for that purpose. (Or you may encounter a special plate made with a central niche for the artichoke, a niche for a small bowl of sauce, and a sort of moat all around on which the leaves are to be discarded.) Continue eating the leaves until the prickly "choke" is revealed -- this is the point when it is clear you have a species of thistle in front of you. Switch to fork and knife, first to remove the choke, then to eat the heart and base.
Asparagus
Asparagus may be eaten with the fingers as long as it is not covered with sauce or otherwise prepared so it is too mushy to pick up easily. Of course, it is also just fine to use a fork and knife to eat asparagus, even when it is perfectly al dente and sauce-free. But you might appreciate getting to act like a rebel without breaking any rules.
Bacon
When bacon is cooked until it is very crisp, and there is no danger of getting the fingers wet with grease, it is okay to pick it up to eat it. This is an instance of practicality winning out over decorum, since trying to cut a crisp piece of bacon usually results in crushing it into shards that are quite difficult to round up onto a fork.
Bread
Bread must always be broken, never cut with a knife. Tear off a piece that is no bigger than two bites worth and eat that before tearing off another. If butter is provided (and at formal events it customarily is not), butter the small piece just before eating it. There is an exception to this rule: if you are served a hot roll, it is permissible to tear (not cut) the whole roll lengthwise down the middle and place a pat of butter inside to melt.
Cookies
It is never necessary to try to eat the cookie that comes as a garnish to your dessert with a spoon. Unless it has fallen so far into the chocolate sauce that there isn't a clean corner by which to pick it up.
Corn on the Cob
It is unlikely that it will be served at a formal event, but if you encounter corn on the cob, it may be picked up and eaten. The approved method of doing so is to butter one or two rows at a time and to eat across the cob cleanly.
Chips, French Fries, Fried Chicken, and Hamburgers
All these items (which could also probably be classified as "fast foods") simply will not be served in a formal setting. Most are intended to be eaten with the hands, although a particularly messy hamburger could be approached with fork and knife, and steak fries (the thick-cut, less crispy variety) may be best eaten with a fork.
Hors d'Oeuvres, Canapes, Crudités
Almost everything that is served at a cocktail party or during a pre-meal cocktail hour is intended to be eaten with the fingers. Some of these foods make appearances at regular meals as well (although not often very formal ones). When they do, it is still permissible to use the fingers to eat them. This includes olives, pickles, nuts, deviled eggs, and chips.
Sandwiches
The straightforward sandwich -- that is, any sandwich that is not open-faced, not too tall to fit in the mouth, not saturated with dripping sauces or loaded with mushy fillings -- is intended to be picked up and eaten. Otherwise use fork and knife.
Small Fruits and Berries on the Stem
If you are served strawberries with the hulls on, cherries with stems, or grapes in bunches, then it is okay to eat them with your fingers. Otherwise, as with all berries, the utensil of choice is a spoon. In the case of grapes, you may encounter a special scissors, to be used to cut off a small cluster from the bunch. If not, tear a portion from the whole, rather than plucking off single grapes, which leaves a cluster of unattractive bare stems on the serving platter.
The Secret of the Formal Place Setting
There is a general consensus among writers of etiquette manuals that too many people are afraid they will fail to choose the proper utensil for the appropriate stage of the meal. Book after book provides reassurance on this point: use the outermost utensil or utensils, as necessary, one set for each course, and you can't go wrong (unless the table has been improperly laid to start out with). For a formal place setting, you will receive exactly as much silverware as you will need, arranged in precisely the right order. Good etiquette requires you to assume (and this ought to ease most people's worries) that the host has correctly assigned each utensil to its task, rather than attempt to point out that a fish fork is improperly being supplied for your salad. As each course is finished, the silverware will be removed with the dish, leaving you with a clean slate, all ready for the next item to arrive. Common sense forbids arranging battalions of forks and knives at the sides of the plate, so on the extremely rare occasions that more than three or four courses are planned, new silverware will be brought to you after all of the original setting has been used.

In this 1902 photograph from Mrs. Seely's Cook-Book (with Chapters on Domestic Servants, their Rights and Duties), the proper place setting shown is little different from the examples provided in Judith Martin's "Miss Manners" etiquette books, in spite of the fact that it is nearly a century old. The plate in this setting is known as a "service plate," and is never actually eaten from. It will either be removed when the first course is brought, or the dish will be set on top of it. A person faced with this array can expect to dine on:
Oysters, as appetizer
Use the small fork angled into the soupspoon at right. This is the one exception to the rule of placing forks to the left of the plate.
Soup
The soupspoon is commonly the only spoon provided for the initial place setting.
Salad
Note the thicker tine at the left of the fork, which strengthens the tool -- for right handed people -- for use in cutting large salad greens without having to resort to the knife.
Fish
Both a fork and a knife are provided for fish. Sometimes the fish knife has a silver blade, because fish, which is often served with lemon, reacts with the steel in old knife blades, causing an unpleasant taste (the invention of stainless steel in the 1920s made this problem obsolete). The fish fork is usually shorter than the meat fork.
Meat
The inner fork and knife are provided for the meat course of the meal.
Dessert
In this case, the dessert utensils will be brought in with the dessert. However, you may encounter the dessert spoon -- and fork, if needed - as part of the initial place setting. They would be placed horizontally over the plate and parallel to each other, with the bowl of the spoon pointing to the left and the tines of the fork pointing right. When coffee and tea are served, a teaspoon will be provided; it is brought in on the saucer.
How to Use a Napkin
Using the napkin at formal occasions, as with much else associated with etiquette, should be a delicate affair. It is meant only to be dabbed at the lips and should not get dirty in the process. It might seem that the napkin is provided precisely so that it can help the diner clean up any mess that might occur during the course of the meal. Of course, this was its original use, (once the tablecloth itself ceased to be used as a napkin), and at an informal occasion such as a barbeque, it still performs this service. But the more formal the event, the more vestigial the presence of the napkin, because the purpose of nearly every aspect of table manners is to preserve cleanliness and proper appearance. If all other elements of the meal are going well, there will be no danger of smudging the linen.
To Start
As soon as you are seated, remove the napkin from your place setting, unfold it, and put it in your lap. At some very formal restaurants, the waiter may do this for the diners, but it is not inappropriate to place your own napkin in your lap, even when this is the case. If your napkin falls on the floor during a very formal event, do not retrieve it. You should be able to signal a member of the serving staff that you need a fresh one.
To Finish
When you leave the table at the end of the meal, place your napkin loosely next to your plate. It should not be crumpled or twisted, which would reveal untidiness or nervousness, respectively; nor should it be folded, which might be seen as an implication that you think your hosts might reuse it without washing. The napkin must also not be left on the chair. There is a European superstition that a diner who leaves the napkin on his chair will never sit at that table again, but other, less supernatural, reasons are often cited for this: it might seem as if you have an inappropriately dirty napkin to hide -- or even that you are trying to run off with the table linens.
Until Next Month,
Best Wishes,

Stephen Scott, Regal Titles
http://www.RegalTitles.com