We leverage the Enhanced Page Layout Editor to customize and create page layouts.
Field Level Security (FLS) determines who can see and edit fields for an object. In this lesson we work through the process of setting FLS on various fields on an object. We also view Field Accessibility.
Page layouts are assigned by Record Type and Profile. We work through the steps of assigning page layouts in this lesson.
You can introduce Record Types for Custom Objects in Salesforce. Although this isn't a decision to be taken lightly, circumstances may dictate that there's no better option than implementing Record Types on your custom object - such as needing to provide different page layouts for different users...