Start with the joke's essential words and remove setup the image already supplies. Use a large type size, strong contrast, and enough space from the edges that platform cropping will not remove the text. Avoid tiny captions that are readable only while editing.
Preview the result from the meme generator at the size it will appear in a feed, not just at full resolution. Check whether the text covers a face or important visual detail. If the punchline requires a paragraph, consider a different format rather than shrinking the font.
Export and inspect the actual file for cropping, blur, and color changes before sharing.