Whenever you discover three dots next to a word in your dictionary, make an index card with the word on one side and the translation on the other. Drill your vocabulary cards every day. Entries you make for grammar points should explain the syntax of a particular word or phrase and cite the section of Allen and Greenough that explains the point. Note, the text we are using provides vocabulary and grammar notes. These are handy, but not sufficient.
Petronian vocabulary is extraordinarily rich and desrves to be pursued.
You should look up words in the Oxford Latin Dictionary to get complete entries on important words. Important words tend to be the ones you find most puzzling. Break the text you are reading down into sentences. Look up and take notes on the vocabulary and grammar points you need to know to translate the sentence. Repeat the process for the next sentence.