Begin with breakpoints based on content, not gadgets. Ask what layouts the content demands: single column for reading, two columns for browsing, three or four for dashboards. Define container widths and max line lengths that prevent stretched paragraphs on wide displays. Use fluid sizing between breakpoints to avoid jarring jumps.

Columns and gutters form the visible rhythm. Common choices include 12 columns on desktop and 4–6 on mobile, but the numbers matter less than consistency. Keep gutters generous enough to separate elements while leaving room for breathing margins. Establish a spacing scale (e.g., 4, 8, 12, 16…) and use it everywhere—padding, gaps, margins—to simplify decisions and reduce one-off values.

Alignment is where grids earn trust. Align text baselines across modules, snap media to column edges, and align action buttons with form fields. Micro-misalignment creates low-level discomfort that users can’t name but feel. Baseline grids are especially helpful for long-form reading and complex lists. Use optical alignment for punctuation and numerals so tables and price lists feel clean.

Use layout primitives—Stack, Cluster, Sidebar, Cover, Switcher—to solve common problems without reinventing patterns. A Stack controls vertical rhythm; a Cluster handles groups of small items; a Sidebar balances main and aside content; a Cover centers a hero; a Switcher toggles between one and many columns responsively. Encode these as components to make good layout the default and to reduce CSS drift.

Test with real content and stress cases: long titles, tiny images, empty states, and translated strings. Try extreme zoom levels and reduced motion settings. If the grid holds, the design feels stable. When it breaks, adjust rules rather than patching screens one by one. Your goal is a system that guides, not a set of cages that restrict. Don’t forget density modes. Some users prefer roomy layouts; others want information-dense screens. Define compact, comfortable, and spacious presets that scale spacing and typography together. For complex apps, allow sections to collapse or switch layouts (cards to list) without breaking overall alignment. Finally, document patterns with do/don’t examples. Show how to place forms, tables, and media galleries on the grid. Explain exceptions—edge-to-edge imagery, modal widths, full-bleed sections—so designers know when to break rules on purpose. A well-tuned grid makes your product feel stable today and adaptable tomorrow. When everyone plays by the same simple rules, complexity stays manageable and quality scales.