Don't wait to stake and trellis your tomatoes until they are large! It is much easier start when they are a foot tall and you can sucker as you go along.
You will want to space plants 18-24 inches apart in the row and drive a stake in every other plant or every three plants. Place the stake 3-4 inches from the base of the plant on the side away from the first bloom cluster to keep from trapping the fruit between the plant and the stake. You will want to use sturdy wooden or metal stakes 6 to 7 feet long for indeterminate varieties and 4 feet for determinate varieties. If you use wooden stakes think about using metal stakes every four or five stakes to make the trellis stronger, or at least for end posts.
- Drive your stakes 1 foot into the ground between every other plant.
- On each end of the row use a stronger stake such as a metal T post.
- When the plants are about 12 inches tall, before they fall over, begin the weave at 8-10 inches off the ground.
- Use a strong durable 'tomato twine' which comes in a box that attaches at your belt.
- Tie the twine to an end stake and sweep the twine past the two plants in front of you. Then cross in front of the next stake and loop the twine around the back of the stake and pull it tight.
- Use your forefinger and thumb of the hand not holding the string to keep the sting tense and pull the sting out in front of the next set of plants.
- Hold to post with the fingers of your non string hand and loop the string around the post.
- Make sure to pull the twine tight as you go.
- Proceed along the row and at the end of the row tie off to the end stake and then loop back the other direction until you are back to where you started.
- Tie the twine to the first stake.
- It is easier to weave the twine if you thread the end through a 12-36 inch piece of plastic pipe. This will act like an extension of your arm so you don't have to do gymnastics to loop around the posts low to the ground.
- After a week or two when the plants have grown add another layer of twine 6-8 inches above the last.
- Repeat until you reach the top of your stakes.
You are sandwiching the plants between two walls or baskets of twine. This will keep the plants upright and keep them from cascading out into the rows. Not only will this make it much easier for you to harvest, it is important for managing plant diseases. Most tomato plant diseases like a moist environment. When plants are upright, well-spaced and pruned it is easier for the air to come in and dry off the leaves.
There are other ways to trellis your tomatoes. Growers use cages, individual stakes and for high tunnels you can increase your production with trellises that have wires extending high into the tunnel to a cross wire or other structure. For the field the 'Florida' or 'Basket' weave is common because it is labor saving. It is also easier to sanitize stakes than wire cages at the end of the season which is important to prevent transferring diseases to next year's crop.
Take a look at these videos to see the basket weave in action.
Growing Fresh Market Tomatoes, 2010. The Wisconsin Farm Center, UWEX Publication A3904-02
Caring for the Tomato Crop, 2012. Growing for Market, Pam Dawling.