What is proper etiquette for eating toast?

Consuming toast can vary slightly by culture or nation. In the US, a simple guide regarding a single slice of standard-sized bread would involve using a bread dish in a more formal environment, to using your main dining plate in an environment such as home.

Using a single slice, depending on preference, it's certainly permissible to butter the entire slice, always making sure that the knife you use to remove your butter patty, is transferred to your butter plate, then returned to the butter. At no time should the knife you use to remove butter from the main block, be used for your dining. The point is that your 'used' knife could transfer anything from bread crumbs, to jam, to whatever else it may be you've had on your plate. Always 'protect' the butter's cleanliness.

Once you've buttered the single slice, rather than lifting the entire slice to your mouth, slice the toast in half. But keep in mind, once you've used that knife for anything, it should never be used again for removing butter from its original pristine block or tub.

If you think about this, it does make sense as there's the possibility of transferring bacterial germs which can infect the butter, which in turn distributes those germs to others. Continually reaching over to scrape amounts of butter from the tub, then rubbing it on your toast and returning back to the tub again is an absolute 'no no!' Instead, scrape what you anticipate to use, or even slightly more from the block, smooth it onto your plate, and then pass the tub or block to others to use. Then use your own knife to attend to your toast.

Even if you see others repeatedly use their knives, moving back and forth from butter to toast, do not consider this as acceptable for yourself. Just because everyone else is doing it, isn't a license for you to lower your consideration towards others. In fact, it may very well be commented upon after you leave as to how considerate you were, by the fact you showed poise, grace, and respect by protecting the integrity of the butter for others.

The same applies to hot drinks and sugar: Never re-use the same spoon which you've already dipped into your hot drink to remove sugar from the bowl. It can dampen the sugar, as well as stain it with your tea or coffee. And, of course, the same methodologies apply in considering the transference of germs.

In some cultures, large portions of lightly toasted breads are passed around a table for others to share. Each diner holds the bread with their left hand and tears away pieces with their right hand. In that 'toast' scenario, the bread should be placed either on your plate or beside your plate on the table. Butter, jam, Nutella, or other spreads should be removed from their plates or containers with your knife or spoon (whichever is provided), and placed directly upon your plate - never directly on the toasted bread. Each time you wish to have more of the toasted bread, you tear off a portion, returning the larger piece to the side of the plate or table, and then spread your condiment onto the piece you're about to consume.

And in a final act of gentility; in some cultures, (even occasionally including the States), it is a gesture of kindness to lightly butter a slice and then present it to the lady nearest you, or your wife, girlfriend, etc. Your gracious manners will always be noted....(just make certain your hands are immaculate and your nails are clean)!