If testing for covid, how soon after symptoms appear is it best to get tested to prevent a false negative from occuring? like, do you get tested as soon as symptoms appear or wait a few days?

Early treatment protocols benefit from early recognition of this or any disease and make early testing preferred. The positivity rate in my state rose from a stable 4% to 15-18% from April to July and remains there now. I see no benefit in waiting if you consider exposures/symptoms and benefit of early treatment to avoid a severe outcome.

Testing has been shown to be most accurate 3-5 days after a known or suspected exposure, or 3-5 days after symptoms begin. If you are very ill, you should also contact your doctor to be fully evaluated, or go to the ER if you have difficulty breathing or chest pain (then don't wait the 3-5 days). PCR/molecular testing is more accurate than rapid testing most times.