Deciphering old genealogy documents can be frustrating, fun, and depending on what you find, full of surprises! Sometimes, the problem in decoding the handwriting is that the image itself is faded or blurry, and changing the exposure of the image may help. I often put hard-to-read documents into my favorite editing software, GIMP, then decrease the exposure, and zoom in to view the document at a larger size. Or, if the document is on my iPhone, I can take a screenshot of it, lower the exposure in my iPhone's built-in photo editor, and zoom in to get a close-up view.
Sometimes the handwriting on a document is easy to read, but I am unfamiliar with the styling of the letters. Genealogy handwriting detectives may want to familiarize themselves with the historic handwriting styles of Round Hand, Secretary Hand, and Italic Hand. Also bear in mind that some of the words on the genealogy document may no longer be used. If you are struggling to decipher an old death certificate, you may want to brush up on archaic medical terms. Even some place names are no longer in use today. For example, if you cannot figure out the name of the partially-illegible Virginia county on your ancestor's birth certificate, it may be because you are only focusing on the counties that exist today, instead of counties that existed back when your ancestor was born. And remember, if you can clearly read a word but it still makes no sense, it may be because you are looking at an acronym instead of a word.
If you cannot decipher the document yourself, try posting it to a website or forum dedicated to decoding handwriting. Two public online forums where you can upload hard-to-read handwriting are Reddit.com/r/Genealogy and Reddit.com/r/Cursive. You can also seek help through the private Facebook group called "Deciphering Genealogy Script."