Coherence is the quality that makes your writing understandable. Sentences within a paragraph need to connect to each other and work together as a whole. One of the best ways to achieve coherency is to use transition words. These words create bridges from one sentence to the next. You can use transition words that show order (first, second, third); spatial relationships (above, below) or logic (furthermore, in addition, in fact). Also, in writing a paragraph, using a consistent verb tense and point of view are important ingredients for coherency.