The classic one in regard to gods is from the letter to Menoeceus. This is Bailey, and he uses the word "conceptions" but that prejudges the issue; other translators use preconceptions or anticipations: "The things which I used unceasingly to commend to you, these do and practice, considering them to be the first principles of the good life. First of all believe that god is a being immortal and blessed, even as the common idea of a god is engraved on men’s minds, and do not assign to him anything alien to his immortality or ill-suited to his blessedness: but believe about him everything that can uphold his blessedness and immortality. For gods there are, since the knowledge of them is by clear vision. But they are not such as the many believe them to be: for indeed they do not consistently represent them as they believe them to be. And the impious man is not he who popularly denies the gods of the many, but he who attaches to the gods the beliefs of the many. For the statements of the many about the gods are not conceptions derived from sensation, but false suppositions, according to which the greatest misfortunes befall the wicked and the greatest blessings (the good) by the gift of the gods. For men being accustomed always to their own virtues welcome those like themselves, but regard all that is not of their nature as alien."
Example 2 is from the letter to Herodotus as to time. Here again is Bailey, prejudging and using the word conception again:
Moreover, you must firmly grasp this point as well; we must not look for time, as we do for all other things which we look for in an object, by referring them to the general conceptions which we perceive in our own minds, but we must take the direct intuition, in accordance with which we speak of “a long time” or “a short time,” and examine it, applying our intuition to time as we do to other things. Neither must we search for expressions as likely to be better, but employ just those which are in common use about it.
Nor again must we predicate of time anything else as having the same essential nature as this special perception, as some people do, but we must turn our thoughts particularly to that only with which we associate this peculiar perception and by which we measure it. For indeed this requires no demonstration, but only reflection, to show that it is with days and nights and their divisions that we associate it and likewise also with internal feelings or absence of feeling, and with movements and states of rest; in connection with these last again we think of this very perception as a peculiar kind of accident, and in virtue of this we call it time.
The third is in relation to justice - from Dewitt
Also check this page for the placement of preconception: http://wiki.epicurism.info/Principal_Doctrine_38/