There are as many designs of tomato cages as there are preferences to their use. There is a variety of materials to use for tomato cages, as well. You need to consider what you want out of your tomato supports. How long do you want them to last? Wooden crates can be built or purchased and are relatively inexpensive but the wood will eventually rot so you may get fewer years of use from this type of support. Wire supports will last longer but sometimes they aren’t strong enough to support large tomato plants. PVC works well but sometimes take longer to put together and the sun will eventually weaken them. You also have to consider where you will store the cages when they aren’t being used. 
- How much room do you have?
- Can the cage be dismantled so it will store in a smaller spot?
Now you need to consider design:
- How easy will it be to prune and harvest your tomatoes in the cage you use?
- Do you need the bottom open to allow for easy weeding and watering?
- Do you need the top more open to make harvesting your ripe tomatoes easier?
Once you have determined what design and material you want to use, there are numerous sites that will give you detailed instructions on building your tomato cages and pros and cons of the multitude of designs available.
One thing is certain, you will need to support your tomatoes to get a healthier and more abundant harvest. Enjoy!