I wrote my novel on a Mac computer using MS Word, which automatically checked each chapter as I wrote it for spelling and/or grammatical errors. That was my first line of defense against those types of mistakes. However even MS Word occasionally overlooks an error, allowing the wrong word instead of suggesting the right one, as long as it is spelled correctly. This often happens where the word in question doesn't constitute a grammatical error. ‘The soccer match was one by our team’ is a good example of this, where ‘one’ should be ‘won’. Spell-checkers don’t seem to be able to detect errors with homonyms. (E.g. one, won; beach, beech; cereal, serial, etc.)
The way I got around this was proofreading aloud. When you read silently, you tend to unintentionally skip over words, including errors. This is because our brain ‘auto-corrects’ things for us without us realizing it. (Just ‘Google’ the word ‘typoglycemia’ for a better explanation of this. You can also find this word defined on ‘Wikipedia’.)
Also, the longer the text, the more tired or lazy our brain becomes as we attempt to edit it. Instead of taking the trouble to read each and every word, our ever efficient brain automatically predicts what is written, especially in the case of prepositions and conjunctions and so on, and naturally skips to the next ‘real’ word. This is a skill we picked up when we first learned to read.