When sentences and paragraphs flow from one to another without discernible bumps, gaps, or shifts, they are said to be coherent. Coherence can be improved by strengthening the various ties between old information and new. Here are some techniques for strengthening those ties:

Linking ideas to the topic sentence

Repeating key words with synonyms

Repeating key words exactly

Using parallel structures

Maintaining consistency

Using transitions between sentences

Using transitions between paragraphs