Your backyard tomatoes should now be tall enough to begin staking: we highly recommend staking and training tomatoes early, while they are small. If you wait until they flop, you risk breaking the tender stalks.
Also, keep on pinching the suckers of your heirloom tomato varieties. Suckers are the growth that comes out where the big leaf attaches to the main stem of the plant. By plucking off these suckers you will increase your chances of big fruit and a bountiful harvest.