Is it necessary to prepare the text before davening?

In earlier times, when people did not have access to siddurim, there was an obligation to prepare before reciting tefillos that were davened infrequently. Even if one davens with a siddur, passages with terms that are hard to translate should be prepared in advance. Based on this need for preparation, some poskim say that a chazan must daven his own quiet Shemoneh Esrei with the same nusach that he will use to recite Chazoras Hashatz. The rationale is that if he were to daven in his own nusach, he would not be fully prepared for Chazoras Hashatz. Others say that the concept of preparing for davening is to avoid making actual mistakes in the davening. Confusing nuschaos is not as consequential, since one is yotzei regardless of the nusach that he uses for davening.

סי' ק' ס"א ס"ק א' וג ביאורים ומוספים דרשו 3

What is the minimum amount of kavanah necessary for Shemoneh Esrei?

A person must have proper kavanah throughout Shemoneh Esrei. Proper kavanah means understanding the meaning of the words. If it is difficult to keep one’s focus for the entire Shemoneh Esrei, one should focus at least on the first brocha of Avos. It is of primary importance to maintain one’s focus throughout the first brocha. The poskim disagree about whether kavanah is necessary for each word of Avos or whether it is sufficient to focus on the main ideas of the brocha.  It is also crucial for a person to have kavanah for the brocha of Modim.

סי' ק"א ס"א ס"ק ב' ביה"ל ד"ה המתפלל ביאורים ומוספים דרשו 5

Does tefilla without kavanah have any significance? 

If a person does not have kavanah during the first brocha, he is not yotzei. Shulchon Aruch rules that he must repeat Shemoneh Esrei. Rema says it would be pointless for a person in that situation to repeat Shemoneh Esrei. He explains that if the person did not have kavanah the first time, there is no reason to believe that he will have kavanah the second time. If, upon completing Avos, a person realized that he did not have kavanah, the poskim question the value of his finishing Shemoneh Esrei. If he will not be yotzei anyway, would the brochos he adds be brochos l’votalah? Some answer that he may finish Shemoneh Esrei, since a tefilla -- even if it lacks kavanah -- is still a tefilla.

ס"א ביה"ל ד"ה והאידנא ביאורים ומוספים דרשו 11

• A person who has been drinking wine or other intoxicating beverages may not daven.

• Later Achronim qualify that some of the halachos regarding davening after drinking pertained to earlier generations that davened with a high level of kavanah. Several factors make these halachos 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 are in control of their thoughts and speech.

• 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. 

• Should one answer Amen when he hears another person completing a brocha of Shemoneh Esrei?

• Why is it preferable to daven in Lashon Kodesh?

• What are the pitfalls of davening in another language?