Common MUST-KNOW T-Codes in MM for a FICO Consultant

Purchase Requisition
ME51N : Create Purchase Requisition
ME53N : Display Purchase Requisition
ME52N : Change Purchase Requisition

Purchase Order
ME21N : Create Purchase Order
ME22N : Change Purchase Order
ME23N : Display Purchase Order
ME2N : List by PO Number

Release PO
ME29N : To release PO (Part of an approval procedure/workflow/Level of Approval)

Goods Receipt
MIGO : Goods Receipt

Incoming Invoice
MIRO : Enter Incoming Invoice