To forego means “to go before” – the matching fore in forego and before is a handy way to remember the correct form:
We have decided to proceed, for the foregoing reasons…
Its past tense and past participial forms (forewent and foregone, respectively) are rarely deployed, except the latter’s use in the phrase foregone conclusion – where the conclusion has “gone before” the question.
To forgo means “to abstain, renounce, do without”, especially something pleasurable or advantageous.
A prior commitment led me to forgo the picnic.
Forgone Forwent is its past tense form; forwent forgone is its past participle.
An overlap complicates things slightly: forego is a variant spelling of forgo (“abstain, renounce, do without”) but the reverse is not the case, so avoiding this variation will help retain a useful distinction.
Both forms together, with dessert:
The meal was most substantial, and the size of the foregoing courses led me to forgo dessert, at least for half an hour.