What are some common solutions to address the 'allowed memory size exhausted' error?

Several solutions exist. 1) Disable or uninstall unnecessary plugins. 2) Reduce the number of themes. 3) Optimize images by compressing them and using appropriate formats (WebP). 4) Limit the number of active WordPress comments. 5) Consider using a caching plugin to reduce database load. 6) Upgrade your server's hardware if possible.