Trimming the fingernails and toenails, trimming the upper lip beard, removing the armpit hair, and shaving the pubic hair before entering the Ihram state if it is expected that these things will become necessary while one is in the Ihram state. If this is not expected, the said is not considered a Sunnah deed.

Washing the whole body before entering the Ihram state (also applies to women who are having their menstrual or postpartum bleeding, as it is mainly for cleansing the body and not for ritual cleansing).

Applying perfume or the like to the body before entering the Ihram state (not on the Ihram clothes! If the smell/perfume passes from the body to the clothing, this is not a problem).
Note: Women in general, according to Islamic rules, must take care that the smell of perfumes is not perceptible to strange men.

For men: putting on two white, clean cloths.

The grasping of intention (Niyya) and thus entering the Ihram state after an obligatory or naafilage prayer.

Repeating and increasing the saying of the Talbiyah. The Talbiyah must be said at least once at the border (Al-Miiqaat) before crossing it, if one has made the appropriate intention of Hajj or 'Umrah, and thus enters the Ihram state.

Note: During the 'Umrah, the Talbiyah is said until the beginning of the Tawaf. During Hajj, the Talbiyah is said until the beginning of the throwing of the stones (Jamratu-l 'Aqabah) on the morning of the 10th day of the month of Dhu l-Hijjah.
For men, the Talbiyah is spoken loudly and audibly according to the Sunnah. For women, the Talbiyah is not spoken in a way that is audible to others. The talbiyah is the utterance of the words:

Talbiyah

Saying supplications (Du'aa) as well as asking Allah for honor and salvation for Prophet Muhammad ﷺ at the end of saying the Talbiyah during its temporary interruption.

Speaking the words:

❃ إنّ مَحَلِّي حيثُ تحبَسْتَني ❃
❃ Inna mahillii haithu tahbisunii ❃
❃ My exit from the state of Ihram shall be in the place where You stop me ❃

These words should only be spoken by the one entering the Ihram state who fears not being able to complete his pilgrimage due to illness or the like. This is especially true for women who are facing the onset of their menstrual period. In the case of being prevented from performing the Hajj or the 'Umrah, for example, due to illness or the like, no sacrifice is then necessary in order to leave the Ihram state.