Hashem spoke to Moses to give the instruction to celebrate this holy day, to the Children of Israel in Vayikra/Leviticus 23:23-25.
"In the seventh month, on the first of the month, there shall be a rest day for you, a remembrance with shofar blasts, a holy convocation. You shall not do any laborious work, and you shall offer a fire-offering to Hashem."
It is therefore essential to HEAR the blasts of the shofar.
Another component of preparation for Rosh Hashanah is to ask forgiveness for all the wrongs done to others and sins committed during the past year. (and be willing and quick to forgive others!)
We want to begin a new year with a clean slate and be inscribed in the Book of Life.
Hearing the Shofar
The instruction is to HEAR the shofar.
The prescribed shofar to use for the blasting is a curved ram's horn, but the traditions of different groups vary.
For use in the Tabernacle and the Temple, Hashem said to "Make for yourself two silver trumpets...", in Bamidbar/Numbers 10:2.
Traditional Holiday Food
There are several symbolic foods that is eaten on Rosh Hashanah.
Firstly round challah.
Make the blessing and dip a piece of bread into some honey to symbolize our prayer for a sweet year.
Next take a piece of apple, make the blessing, dip in honey and say: "May it be Your will, Hashem, to renew us for a good and sweet new year.
Although Rosh Hashanah is called the 'new year' it is the 1st day of the 7th month (Tishrei). This is the beginning of the Jewish Civil Year.
On the first day of Rosh Hashanah after the afternoon prayer, everyone goes to a body of water that has fish (lake, sea, river or pond) and recite the Tashlich prayers, thereby symbolically casting previous sins into the water and leaving shortcomings behind, thus starting the new year with a clean slate.
There are many unique prayers for Rosh Hashanah, so a special book is used, called the "Machzor".