Monday is Erev Rosh Chodesh Elul. Every Erev Rosh Chodesh is considered a special time for teshuva and is called Yom Kippur Koton. There is a special order of prayers added by Mincha, which is said by many people. Additionally, some fast a whole day or a half-day, till after Mincha. Those that fast read Vayichal and say Aneinu, like on a regular fast day.
Mateh Epraim says that on Erev Rosh Chodesh Elul, many who never say these prayers the rest of the year, recite them now. Shaar Yisoschor explains, because on this day (40 days before Yom Kippur) Hashem forgave Klal Yisroel for the golden calf, and Moshe Rabbeinu ascended to receive the second set of Luchos. In Eretz Yisroel, many go to the Chevron, the Meoras Hamachpela, or to Meron, by Rebbe Shimon bar Yochai, to recite the Yom Kippur Koton tefilos.
Nitei Gavriel brings down, whether or not one says the Yom Kippur Koton tefilos, EVERYONE has to do teshuva,