Sea-farers. Only when they reach their final destination on land.
Travelers in the wilderness. Only when they reach their final destination of settlement.
Healed from sickness. Only when he is strong and walking around.
Released from prison. Only when waiting a potential death sentence or when the prison itself is a dangerous place. (Excluding a day-jail for petty crimes.) (ShA1 – MB1,2,3 – BeH ”chavush”)
Since the above salvations could be life-threatening, Chazal instituted a beracha when the threat is no longer, even if no danger actually happened. (BeH “yor’day”)
Children do not say this beracha, even for chinuch. (MB3)
The minhag is that women do not say this beracha. Some say she should say the beracha in front of 10 people – at least some women and 1 man. (MB3)
L’chatchila, stand when reciting the beracha as follows: Boruch atta Hashem Elokaynu Melech ha’olam hagomel l’chayovim tovos sheg’molani kol tov. The listeners should respond, “Mi sheg’mol’cha kol tov, hu yigmol’cha kol tov selah”. (ShA2 – MB4)
Hagomel should be recited in the presence of 10 (including the ba’al hanais), of which 2 are scholars of halacha. The minhag is to say the beracha after Krias Hatorah. (ShA3)
If you do not have 10 people, do not say the beracha with the Shem. If you do not have 2 scholars, you do say the beracha normally. If there are not 10 people, wait to say the beracha for 30 days – maybe you will get 10 people. (ShA3 – MB8)
You can be motzi someone who also needs to say Hagomel, provided both you and he had kavana to be yotzay. (ShA5)
It is proper not to delay the beracha for 3 days. This is more important than the minhag to recite Hagomel with a sefer Torah. Therefore, if he was set free from prison on Monday after Krias Hatorah, he should say the beracha with 10 people without the sefer Torah – don’t wait until Thursday. B'dieved, if you delayed the beracha, you can say the beracha as long as you like. (ShA6 – MB20)
The minhag Ashkenaz is to say Hagomel only after travelling through a wilderness. Do not bless Hagomel just from one city to the other unless the road is known to be exceptionally dangerous. (ShA7)
How sick is “sick”? Either life threatening (e.g. high fever, internal wound) or sick in bed for 3 days or more. (ShA8 – MB28)
The above mentioned four situations are laav davka. Any other life threatening situation that one is saved from deserves a Birkas Hagomel. Examples: a wall fell on him, trampled or gored by an ox, attacked by a lion, attacked by robbers. Don’t forget the blessing upon seeing the location of the miracle mentioned above in Siman 218. (ShA9 – MB30,32)