SheetWorkflow Guide 
Start Excel Formulas with Clear Inputs and Operators
Every Excel formula begins with an equals sign followed by a calculation or function.
Diagnose External References and Range Errors in Conditional Sums
The source lists references to a closed workbook among the causes of SUMIF and SUMIFS problems.
Keep SUMIFS Criteria Aligned with the Values Being Added
SUMIFS calculates a total only for entries meeting the stated conditions.
Use SUMIFS for a Total That May Gain More Requirements
SUMIFS can handle a single criterion as well as several, so it can provide a consistent structure for conditional totals that may become more detailed later.
Check Argument Order When Moving from SUMIF to SUMIFS
SUMIF adds values according to one criterion, while SUMIFS is designed for multiple criteria.
Use SUMIF for an Excel Total with One Clear Condition
SUMIF provides a conditional total instead of adding every number in a range.
Understand the INDEX-MATCH Alternative to a Dedicated Lookup
INDEX returns information from an array according to a position, while MATCH finds the position of a requested value.
Compare XLOOKUP with the Other Common Lookup Methods
VLOOKUP, XLOOKUP, and the INDEX-MATCH combination all locate related information, but they express the task differently.
Search from the Bottom When the Last Excel Match Matters
Repeated identifiers can occur throughout a list, so the first match may not be the one the analysis needs.
Plan Several Criteria Before Extending an XLOOKUP Formula
XLOOKUP requires a lookup value, a lookup array, and a return array.
