Familiarize yourself with relative pronouns (qui, que, dont, auquel, duquel, etc) which are invaluable in providing the links between the different parts of sentences
Master once and for all those aspects of the agreement of the past participle that the perfect and pluperfect tenses require. The rules of agreement when using either avoir or être as the auxilliary verb are covered, as are those concerning reflexive verbs.
Know how to choose between the perfect and imperfect tenses, learn how to use the very useful pluperfect tense (which is much easier than is often thought), etc.