The President and Congress

• Executive orders and proclamations
• Signing statements
• Vetoes
• Item veto
• Legislative or congressional veto

The tug-of-war between president and Congress: NAIL

• Nominations:  recess appointments. And confirmation hearings not only enable senators to judge the nominees' qualifications but let them send messages to the administration. See Leahy ask Mukasey about torture. See Harkin talk to Solis about disabilities.
• Appropriations:  immigration limitation riders (background)
• Investigations: executive privilege and impeachment. One famous example was the Senate Watergate Committee, in which then-staffer Fred Thompson played a role. Senator Feingold held an oversight hearing on "czars." Congress may also study executive branch operations through the GAO, the CBO, and the CRS.
• Legislation