Constitutional Law
Judicial Review and Justiciability
Start with standing: injury in fact, causation, and redressability. Then ripeness, mootness (with the capable-of-repetition-yet-evading-review exception), and the political question doctrine. These threshold issues are frequently the correct answer when a question seems to invite a merits analysis.
Government Power
For federal action, identify the enumerated power (Commerce Clause, taxing and spending, war powers, treaty power). The Commerce Clause reaches channels of interstate commerce, instrumentalities, and activities substantially affecting interstate commerce - but not noneconomic intrastate activity under the substantial-effects test (Lopez/Morrison). For state action, apply the Dormant Commerce Clause (discrimination against interstate commerce is virtually per se invalid absent a legitimate local purpose) and the Privileges and Immunities Clause of Article IV.
Individual Rights and Equal Protection
Classify the discrimination: suspect (race, national origin, religion, alienage) - strict scrutiny; quasi-suspect (sex, illegitimacy) - intermediate scrutiny; all else - rational basis. Fundamental rights (voting, travel, privacy, marriage) trigger strict scrutiny. Due process protects procedural fairness and substantive liberties; the Bill of Rights applies to states through selective incorporation.
Traps
Watch for state action requirements in equal protection and due process claims - private conduct generally isn't actionable. Also distinguish facial from as-applied challenges, and remember that content-neutral time, place, and manner restrictions on speech need only be narrowly tailored to a significant government interest.
Rule of thumb
Name the right, name the classification, name the standard of review - in that order.