Netilas Yadayim
After saying Modeh Ani, one must wash Netilas Yadayim.
(Although many siddurim print Reishis Chochma right after Modeh Ani, there is a machlokes as to whether or not you are allowed to say pesukim like this before Birchos HaTorah. Therefore, some say waiting and saying Reishis Chochmah is preferable after you have already recited Birchos HaTorah. This was the Minhag of Rav Moshe Feinstein. (Rivevos Efraim 2.2 & 4.474)
There are four reasons for washing hands in the morning.
• during sleep, one’s hands move about and unavoidably touch parts of the body that are not clean (Rosh brachos 23)
• every morning, we are created anew. Therefore, we must thank Hashem and recite blessings in his name. The sages, therefore, instituted the berachos we recited each morning and enacted that every morning when we are about to serve Hashem in prayer, we must sanctify ourselves by washing our hands from a vessel, just as the Kohen must wash his hands from the Kiyor in the beis hamikdash before performing the Avodah. (Teshuvos harashba 1.191)
• every night, an impure spirit rests on one’s hands and does not leave until one pours water on them three times. (Orchos chaim hilchos Netilas yadayim 11)
• when one sleeps at night, his soul leaves him, causing an impure spirit to rest on his entire body. The impure spirit leaves his body when he wakes up but remains on his hands. (Zohar Parshas Vayeshev 184)