Walk-in only. The terrace is the seat to want; expect a wait and full tourist prices in high season.
Les Deux Magots faces the church on Place Saint-Germain des Prés in the 6th arrondissement. Wikipedia dates the café to 1884, when the spot took over a novelty shop named for a play and kept the two Mandarin figures, the deux magots, on the central pillar where they still sit.
It rewards anyone who wants the history with their drink. Sartre and Simone de Beauvoir kept a near-daily table here, and Ernest Hemingway worked on his fiction in the room, per the café's own history. It frustrates anyone chasing a deal: this is a landmark with landmark prices, and the terrace is half the cost of admission.
The café created the Prix des Deux Magots literary prize in 1933, a marker of how seriously Saint-Germain took its café-intellectual culture.
The interior keeps its early-twentieth-century fittings, with the two magot figures watching over the room from the central column. The terrace faces the oldest church in Paris and is the seat most visitors want. Sortiraparis describes it as one of the city's most storied cafés, busiest at breakfast and at the evening aperitif hour.
This is a café and aperitif room rather than a cocktail bar. Order the house hot chocolate, served from a jug and the drink the café is best known for, or a glass of French wine on the terrace. Classic aperitifs and a short cocktail list round out the evening. Expect to pay landmark prices: coffee runs around €7 and the hot chocolate around €9.