If you see the Yam Suf or Jordan River it is fitting to thank and praise Hashem for the miraculous intervention He performed for us with these bodies of water. Do not say a blessing with the Shem unless you see the actual place of crossing. (BeH “k’gon”)
After a miracle happens to you, say the blessing “…she’ossah li nais bamakom hazeh” when you arrive at that location again after 30 days. (This 30-day rule applies to all the blessings in this siman.) (ShA4 – MB15)
If the miracle happened to your father or grandfather, mother or grandmother, the nusach of the blessing is “…she’ossah nais l’_____ bamakom hazeh”. (ShA4 – MB16,17 – BeH “v’chol”)
If you are from a third generation, you will only say the beracha if your parent was born after the nais happened to your great-grandparents. (MB16)
A student blesses upon seeing the place that a miracle happened to his rebbi muvhak. (ShA6 – MB20)
The poskim argue about the requirement of a beracha when the salvation happened in an ordinary way. For example, thieves entered at night but did not kill anyone. Or, a crushing stone fell near your head. Say the beracha without the Shem. However, you should say Birkas Hagomel (with the Shem) after being saved from sakkana in any case. (ShA9 – MB31)
Even if the salvation was not extra ordinary, you are still obligated to praise the Creator for it. The gemara in Shabbos 33b implies that you should do something for the benefit of the public to commemorate the event. (MB32 – BaH4)
After a nais, you should give tzedoka to Torah learners according to your means. You should state: “This is for tzedoka and it should be considered in place of a Korban-Todah that I would have brought had the Bais Hamikdash been standing. It is fitting to recite the parsha of Todah. Make a simcha to thank Hashem and recount His kindness every year on the anniversary. (MB32) LAWS OF THANKSGIVING BLESSINGS