It is customary to say more Tehilim than usual and to read Tikunei Zohar in the month of Elul. For more see:
Uman! Uman! Rosh Hashana explains everything you wanted to know about Uman Rosh Hashana.
Breslov Center: Rav Elazar Kenig on Rosh Hashanah Part I (PDF)
Breslov Center: Rav Elazar Kenig on Rosh Hashanah SPECIAL ADDITIONS (PDF)
Breslov Center: Elul-Tishrei Through Chanukah Customs and Practices (PDF)