If two ideas are not of equal importance, it’s often effective to express the major idea in an independent clause and place the minor ideas in subordinate clauses or phrases. Subordinate clauses, which cannot stand alone, typically begin with a subordinating conjunction or relative pronoun.
Deciding which idea to emphasize is not a matter of right and wrong but is determined by the meaning you intend. Consider the two ideas about chemotherapy and its side effects.
If your purpose is to stress the effectiveness rather than the side effects, subordinate the idea about the side effects.
To focus on the side effects, subordinate the idea about effectiveness.
Exercises:
Identifying sentence emphasis 1
Identifying sentence emphasis 2
Using coordination and subordination 1