The stoning sequence differs between the Day of Sacrifice (10th) and the Days of التشريق (11th-13th). On the 10th of ذو الحجة, only one pillar is stoned: الجمرات al-Aqabah (also called al-Kubra — the largest pillar, located nearest to مكة). You throw 7 pebbles at it, saying 'Allahu Akbar' with each throw.
On the 11th, 12th, and 13th of ذو الحجة, all three pillars are stoned in a specific order, starting from the one farthest from مكة and moving toward مكة: (1) الجمرات al-Sughra (the smallest, farthest from مكة) — 7 pebbles; (2) الجمرات al-Wusta (the middle pillar) — 7 pebbles; (3) الجمرات al-Aqabah / al-Kubra (the largest, nearest to مكة) — 7 pebbles. This order is واجب (واجب) عند جمهور العلماء.
The السنة after stoning al-Sughra is to move to the side, face the القبلةh, raise your hands, and make a lengthy دعاء. Similarly after al-Wusta — stand, face the القبلةh, and make دعاء. However, after stoning al-Aqabah (the final pillar), you do NOT stand for دعاء — you simply leave the area. This follows the exact practice of النبي (صلى الله عليه وسلم). The modern الجمرات bridge is a multi-level structure designed to ease crowding — you may stone from any level, and the pillars are now wall-shaped (not actual pillars) with a basin to catch the pebbles.