I’m a long-term user of Grammarly. This is a program that adds spelling and grammar functionality to other programs, including your browser.
Every week, I receive an e-mail from the company, summarising how many mistakes have been detected and how productive I’ve been compared to other users. But that’s not the full story.
When I give a time, for instance, I’ll write ‘8pm’. Grammarly, by contrast, thinks this should be ‘8 pm’; there appears to be no way – even in the premium version – to permanently ignore this check. There are other occasions where I’m prompted to add or change ‘a’ or ‘the’. In one instance, the program would accept neither ‘the audience is’ nor ‘the audience are’ as correct, telling me to change one to the other.
As such, there is no substitute for checking your work manually. A spelling check will recognise both ‘from’ and ‘form’ as valid words, even the writer meant the other one. A grammar check is unlikely to pick up whether ‘rowing on the lake’ refers to controlling the boat or having an argument.
A good way to do a robust check is to leave the piece aside for a while – I suggest one minute per word – then to read it out loud, which highlights any errors more clearly. If the piece is particularly important, consider asking someone else to read it. There’s no guarantee these steps will eliminate every error, but they will reduce the chances of one cropping up.