There is not one definitive answer to this question. Some people prefer to proofread their own work, while others prefer to have someone else proofread it for them. There are also a number of different techniques that can be used for proofreading, such as reading aloud, reading backwards, or using a proofreading checklist.
If you're proofreading your own work, it can be helpful to take a break between writing and proofreading, so that you can come back to your work with fresh eyes. When you're proofreading, it's important to look for both spelling and grammar mistakes, as well as typos. A good way to catch typos is to read your work aloud, since you're more likely to notice them when you hear them than when you see them.
If you're having someone else proofread your work, make sure to choose someone who you trust to give you honest feedback. It can also be helpful to give them specific instructions on what you're looking for, such as identifying spelling and grammar mistakes, or checking for typos.
Here are a few links with more information on proofreading:
https://www.grammarly.com/blog/proofreading-tips/
https://www.thepunctuationguide.com/proofreading.html
https://www.oxford-royale.com/articles/tips-techniques/effective-proofreading-techniques.html