There is a common mnemonic for this: KISS (Keep It Simple Stupid).

That means simple category names and as few categories as possible. 

You should also avoid breaking user expectations. Organize products in their logical or socially expected categories. Take the example of a TV. Many people expect it to be listed under a category like electronics or a sub-category like home entertainment. Listing it under home appliances is just confusing because people think of a TV as comparable to a phone rather than a microwave or a fridge.

Category names should also be kept as simple as possible. This is not the place to get creative or fancy with naming. It just leads to unnecessary mental effort on the part of your customers. You want them spending money, not performing mental gymnastics trying to figure out the meaning of the names or complex words you’ve used. 

Use simple everyday words. Think clothing instead of apparel, and laptop instead of notebook computer.

 

This also applies to the product layout.

Don’t invent your own custom layout. Nearly all your shoppers have been to other stores and are familiar with the conventional layout. 

This is where the product image is on the left while the price, product description, add to cart button, and the rating are on the right. On mobile the description might be below the product image due to space limitations but the general layout is largely similar. Stick to that layout. Once again, you want customers spending money instead of wasting precious seconds trying to figure out your layout.

It’s also important to keep the order your product attributes consistent. If you list them starting with price, followed by the product description, rating, and finally the add to cart button in that order, stick to it for all products. Don’t switch and put the price below the product description in the next item. Always list those attributes in the same order. It makes scanning easier and quicker.

EXAMPLES