Tip 1: Let the grammar drive your reading (and not vocabulary)!
Latin teachers Scott Ettinger and Sarah Grover at Riverdale Country School in the Bronx, NY acknowledged that when students come across a tough sentence, it can be easy to look up all the unknown vocabulary first. Unfortunately, this often leads to trying to put a sentence together based on the meanings of the words.
Don't do it.
Instead, Ettinger and Grover suggest, let the grammar drive your reading. Before defining words, ask yourself: What cases are the words that especially look like nouns and adjectives? What mood, voice, tense, person, and number are the verbs? Can you tell where clauses—especially subordinate clauses like those beginning with 'when, if, because, who, which'—start and end? That is, the flow of the sentence?
As a language learner, it can be more important to know that a 'puer' (nominative subject) is 'amat'-ing (present, active, indicative, third person, singular verb) a 'puellam' (accusative direct object) than to know the meaning of the words (A boy is loving a girl). You can always look those up.
So, parse if the words you know are sparse! Before flipping the pages of your dictionary (or looking words up online), determine the grammar of the sentence.