What are the four levels of intoxication?

A person who has been drinking wine or other intoxicating beverages may not daven. There are four categories of drinkers: 1) One who drinks exactly a revi’is of wine all at once.  This category also includes those who drink a specific amount of other alcoholic beverages which can bring about the same level of intoxication as a revi’is of wine. Those who do not feel the effects of the revi’is of wine are still included in this category. 2) A shosei—i.e. one who drinks more than a revi’is of wine (or other alcoholic beverages) but still can speak coherently in front of a king; 3) A shikur- i.e. a drunkard. This person is intoxicated to the extent that he can no longer speak coherently in front of a king; 4) A person who has reached a state of drunkenness like that of Lot. This person is so drunk that he is classified as a shoteh. Mitzvos done in that state are not valid.

סצ"ט ס"א ס"ק א' וי"א

Can a person daven after drinking?

Shulchon Aruch rules that those who are in the first two categories should not daven until the effects of the wine wear off. Even if waiting for the wine to wear off would cause the person to miss zman tefilla, he should wait and daven a make-up during the next tefilla. If he davened, his tefilla would be valid b’dieved.  Later Achronim qualify that these halachos pertained to earlier generations that davened with a high level of kavanah. Several factors make this halacha inapplicable in later generations.  First, people generally daven with less kavanah nowadays. In addition, our wines are not as strong as wines in earlier times. People also daven with siddurim today, so less focus is necessary to daven. Given these differences, people today are permitted to daven even if they have been drinking, as long as they feel in control of their thoughts. In addition, contemporary poskim say that one should certainly not miss zman tefilla in order to completely sober up.

ס"א ס"ק ג' וי"ז

Can an intoxicated person recite brochos?

People who are in the third and fourth category may not daven, even nowadays. If they do daven, their tefilla is an abomination and they must daven again. All agree that these people may not daven Shemoneh Esrei. The poskim disagree about whether a shosei or shikur may recite Kriyas Shema. Therefore, a person should not drink before reciting Kriyas Shema. If he did drink, he should not miss zman Kriyas Shema while waiting to become sober. The poskim  also disagree about whether a shikur may recite brochos. All agree that if a person reaches the fourth level, everything he recites is invalid.

 ס"א ס"ק ח' ט' וי"א

• A person who is davening Shemoneh Esrei must keep two things in mind: the meaning of the words and the awareness that he is standing before the Shechinah. According to some Achronim, if one is not conscious of standing before the Shechinah, it is as if he did not daven and he must daven again.

• Children below the age of chinuch should not be brought to shul. Their boisterous behavior disturbs the sanctity of the shul and the concentration of those who come to daven. In addition, they become used to acting in a disrespectful manner there, and this habit may continue when they become older.

• A person must daven in a pleading tone, like a poor man who comes knocking at doors to request alms. Aside from the tone a person uses to daven, he must also daven with the attitude that he is coming to the King to ask for what he needs and not just to satisfy his obligation to daven. 

• Is it necessary to prepare the text before davening?

• What is the minimal amount of kavanah necessary for Shemoneh Esrei?

• Does tefilla without kavanah have any significance?