"Audit" is a scary word but what it really means is, "show us how you got these numbers." These agencies aren't out to ruin your life, they just want your tax return to be a good representation of what happened. It's annoying to get these letters, but, in the end, it's not that difficult to respond in most cases.
Figuring out how to respond and how much time it will take depends on the specific forms that are being ask about, but in most cases, the best thing you can do to help future you out is to keep your tax documents and receipts organized as best you can. Even if they aren't as organized as you wish they were, it's still possible to respond to these letters, you may just decide that you don't want to take the time to defend some of the things on your return if you don't end up having access to those records and the expense isn't so large that you want to worry about it.
If you receive a notice or letter from the IRS or a State Department of Revenue, don't hesitate to reach out. Scan or photograph the letter (complete images of the front and back of every page) and send it to your tax advisor or email@example.com.
After we review it we can have a chat and advise you on next steps.