Overview:

In this tutorial I will show you a great way to prune your tomato plants for healthy, prolific harvest.

First I will explain why we prune our tomatoes and the best conditions to do so. I will then show you what to look for and where to prune your plant.

Although the steps are laid out accordingly, It's always wise to read through the entire tutorial before you start hacking away at your beautiful plants.

Note: I use the words suckers, branches and stems interchangeably. Even though I mean pretty much the same thing with all of them, a sucker is a small "new" stem.

Step 1: Gather Tools

As you can see, not too much involved other than a bit of knowledge and a:

Knife or Pruning Scissors
Bucket

I like to use a knife instead of scissors. I find it easier to get into tight spots and "saw" the sucker rather then trying to clip them with a scissors. If you are afraid of the open blade around your fingers, the scissors will work fine.

Step 2: Trimming

My grandma never trimmed her tomato plants, why should I?

Here are a few good reasons:

Low branches stay wet and are great vectors for plant fungus and diseases
Reduce wasted water and nutrients on unproductive branches
Provide maximum nutrients to tomatoes
Easier to find ripe tomatoes

Trimming:

First of all, the goal is to trim all the lower branches to allow good airflow under the plants and help push water and nutrients to the tomatoes.

We will also pinch off all new flowers and tomatoes starting 30-40 days before first frost in your area (emphasis on the top of the plant). This helps the plant use the remaining days to ripen the tomatoes on the plant instead of budding new tomatoes that won't have time to ripen.

The best time to prune is on a dry, warm day. This gives the tomato a good chance of sealing its cut would without any infection.

Find your "main" stem(s). There should be between 1-3 of them. Never cut these.
Find your first tomato or bud.
Cut all larger stems up to your first tomato.
Find small "new" suckers - Cut these (Will be easier to see and less work if you cut large stems first)
Throw cuttings in your bucket

Note: It is worth taking time to prune your plants on a regular basis. This way the suckers won't grow as large- meaning less energy wasted.

You can trim more than just the lower branches, just make sure to leave enough foliage to shade your tomatoes to prevent sun scald.