Remember, a paragraph is a collection of sentences that deal with one main idea. It has three parts.

1. A Topic Sentence that states the main idea–a topic + a claim about the topic.
2.  A couple of Supporting Sentences that tell more about the topic sentence.
3. A Concluding Sentence that wraps everything up–gives advice, makes a prediction, gives an opinion etc.

Because it has special products from Kochi that make great souvenirs. You can hear "Tosa-ben" spoken by the older shopkeepers. Every tourist to Kochi City should be sure to visit Sunday Market. Sakamoto Ryoma was from Kochi.
It's always lively, and right next to Hirome-ichiba and Kochi castle. You can get a real feel of Kochi there.

Step one: Find the topic sentence

What is the subject? What is the main claim? The most logical topic sentence above is: “Every tourist to Kochi city should be sure to visit Sunday Market.”

Also, don’t use the word “I” unless you are really the topic of the paragraph. e.g. “I want to introduce some reasons why every tourist to Kochi should be sure to visit Sunday Market.”

Step two: Find any unrelated sentences

After the topic sentence come the supporting sentences. Are there any sentences not directly related to tourists visiting Sunday Market? In the paragraph above there is one: “Sakamoto Ryoma was from Kochi.” It has nothing to do with Sunday Market. Cut it!

Step three: Make the better paragraph.

(Remember to remove any line-breaks and fix any sentences that start with “Because” or “So”)

Every visitor to Kochi should be sure to visit Sunday Market. It has special products from Kochi that make great souvenirs and you can hear Tosa-ben spoken by the older shopkeepers. It’s always lively, and right next to Hirome-ichiba and Kochi castle. At Sunday Market, visitors can get a real feel of Kochi.

Let’s try it again. Here’s another paragraph in need of your help:

It's a simple way for a single person to eat healthy. 
Being able to buy pre-cut vegetables for just one person is very convenient. You don't have to wear pants if you live alone.
Because there is no kitchen garbage and you don't have to use a knife. 
It's a little more expensive, but there is much less wasted food. 
So you can easily make salads and stir-fry.