229. One should be careful to be "soimech Geulah L'Tefillah" - to begin Sh'mona Esrei immediately upon completing the beracha of "Go'al Yisroel" and not delay even two seconds.

Shulchan Aruch w/Mishnah Brurah 111:1

230. If possible, one should even try to begin Sh'mona Esrei in the same breath as completing "Go'al Yisroel". Therefore, one should take the three steps back and be standing in his place to begin Sh'mona Esrei before saying the words: "Go'al Yisroel".

Shulchan Aruch w/Mishnah Brurah 111:1, Mekor Chaim/Chavas Yair 111:1

231. The posuk of "Hashem Sefosai Tiftach" is considered part of Sh'mona Esrei, and one may not interrupt for anything, including Kaddish or Kedusha, once he has begun Sh'mona Esrei by saying this posuk. Shulchan Aruch w/Mishnah Brurah 111:1

232. At Mincha and Mussaf however, one may add the posuk of "Ki Shem Hashem Ekrah" and that is not considered an interruption. {Note that many nuschaos do not add "Ki Shem Hashem"}. Shulchan Aruch 111:1, see Be'er Haitaiv

233. The posuk of "Hashem Sefosai Tiftach" was added to Sh'mona Esrei by Chazal because it indicates (as intended by Dovid Hamelech in Tehillim 51) that even one who may have sinned "b'meizid" (purposefully), for whom even Korbanos do not atone, may nevertheless accomplish atonement through sincere tefillah. Bais Yosef 111 citing Rabbeinu Yonah

234. If one forgot to say "Hashem Sefosai Tiftach" and began the first Beracha of Sh'mona Esrei, he is yotze, and need not go back or repeat Sh'mona Esrei.

Shulchan Aruch w/Mishnah Brurah 111:1, see Bi'ur Halacha "Chozer V'ome"r

235. If one forgot to say "Ki Shem Hashem Ekrah" at the beginning of Sh'mona Esrei of Mincha or Mussaf, and one has already begun "Hashem Sefosai Tiftach", one does not go back to say it. {Note that many nuschaos do not add "Ki Shem Hashem Ekrah" at all}.

Sefer Meorer Yeshainim 24, Piskei Tshuvos 111:2

236. It is preferable that any preparations one needs to make before Sh'mona Esrei (ie. focusing one's attention and kavannah for the Tefillah), should be made during "Shira Chadasha", or at the latest, during "Tzur Yisroel", but not after "Go'al Yisroel".

Piskei Tshuvos 111:1

237. If one has completed Go'al Yisroel, but has not yet begun Sh'mona Esrei and realizes that the Tzibbur is saying Kaddish, Kedusha, Borchu, or Mod'im one may listen silently, but may not answer. Piskei Tshuvos 111:1, Pri Megadim 47:109:1,2

238. If the Chazzan said the beracha of Go'al Yisroel out loud, and one did not complete his own beracha together with the chazzan, then one may answer Amein to the chazzan's beracha. Shulchan Aruch w/Mishna Brurah 111:1, and 66:MB35

239. If one has not yet davened Krias Sh'ma by Shachris and the tzibbur is starting Sh'mona Esrei, one should not skip  Sh'ma to daven Sh'mona Esrei with the tzibbur, {because being "soimech Geulah L'Tefillah" is more important than tefillah b'tzibbur by Shachris}.

Shulchan Aruch w/Mishna Brurah 111:3

240. However, by Maariv, one should daven Sh'mona Esrei with the tzibbur, and say Krias Sh'ma with all the berachos (that precede and follow Sh'ma), after davening Sh'mona Esrei