Multi-source reasoning gives you two or three tabs — an email, a table, a memo, a set of rules — and questions that can only be answered by combining them. It is the closest thing on the exam to what an analyst actually does, and it punishes reading everything.
Survey the tabs before reading any of them. Fifteen seconds: what is on each tab and what kind of thing it is. You are building an index, not learning the content.
Let the question route you. Most questions need one or two tabs, not all of them. Read the question, decide which tab holds the relevant fact, go there. Students who read all three tabs thoroughly first run out of time and remember the wrong details anyway.
Watch for the deliberate conflict. These sets very often contain a figure in one tab that is updated, corrected or superseded in another — a revised estimate, an exception to a rule, a later email. Finding that conflict is frequently the entire point of the set, and the trap answer is the one built from the superseded number.
The yes/no and true/false grids have no partial credit. Three statements, each to be judged. Judge each one on its own against the text — do not look for a pattern in your answers. Three "yes"es in a row is a perfectly normal answer key.
Distinguish "supported by" from "consistent with". Something can be consistent with the material without being supported by it. The GMAT writes options in both flavours on purpose.
Time. Data Insights is 20 questions in 45 minutes, and a multi-source set is worth several questions off one set of tabs. The reading is amortised — which is exactly why getting the routing right at the start matters more here than anywhere else in the section.