Unlike its PC counterpart, The Sims 3 on Xbox 360 lacks a traditional pause button. However, you can achieve a near-pause effect by manipulating the game speed settings.
At the minimum speed setting, your Sims' actions crawl at a glacial pace—effectively giving you time to plan, queue actions, or step away briefly without missing critical moments.
Simply return to the Game Speed menu and adjust the slider back to your preferred pace. Note that even at the slowest setting, Sims continue to perform actions incrementally, so you may need to fine-tune the speed based on your current needs.