Compress images like crazy with tools like TinyPNG or Shopify's built-in resizer. Resize before upload too.
Choose a lightweight theme, ditch the bells & whistles you don't use. Consider paid themes like Dawn, built for speed.
Every app adds code, use sparingly. Deactivate unused ones, prioritize lightweight options.
Disable features you don't need, like product reviews if you don't have them. Less code, faster load.
Also Minify HTML/CSS/JS (free online tools are there to detect these), enable browser caching, use a CDN if your store's global.