What’s the difference between forgo and forego? It’s a foregone conclusion that there’ll be some confusion, but I’ll forgo further digression to get to the discussion.
To forgo is to do without, or relinquish: “He will forgo the pleasure of her company”; “I’ll forgo the formality of requiring a co-signer.” The present participle is forgoing (“She is forgoing the procedure”), the past-tense form can be forwent (“She forwent the procedure”) or forgone (“She had forgone the procedure”), and one who forgoes is a forgoer. Only the basic verb form, however, is common.
To forego, by contrast, is to go before, to precede. Forego is much less common in usage than forgo, and it generally has a figurative sense, often used in such statements as “Her reputation will forego her” or “Her reputation foregoes her,” meaning that others will have heard about the subject before they meet her.
However, although the past-tense form forewent is rare, the form foregone, and the present participle foregoing are more common than the root word. A phrase I used in the first paragraph, “foregone conclusion,” is applied frequently to indicate that something is implicitly understood to be true; foregoing refers to something that has previously been encountered, as a passage in a document: “The foregoing statement should not be construed as an endorsement.”
To maintain the distinction between the words forgo and forego in your mind, remember these basics: Use forgo or forgoing in the sense of “doing without”; past-tense usage is rare. And though use of forego is unlikely, foregone and foregoing are common terms for reference to something already done.
Or, most simply, think of -fore in before to remind yourself that forego and its variants refer to sequence and that forgo resembles forget, which is often the reason something is left undone.