German Johnson
Beefsteak Tomato in the US

Right, so you'll want to get these beauties started indoors, about six to eight weeks before your last frost date. For those in warmer spots, like USDA Zone 8 or 9, you can get going as early as January or February. Zone 6 and 7 folks are looking at February or March, and if you're in Zone 5, March or April is your window. Sow your seeds a quarter inch (6mm) deep in good seed-starting mix, keep them warm, around 70-75°F (21-24°C), and they'll pop up. It's about 85 days from that little seed to a ripe tomato, so plan ahead.

Once your seedlings have their first true leaves, it's time to prick them out and give them their own small pots. Keep them warm and watered. Before planting them out, harden them off properly over a week or two, gradually introducing them to the outside. When all danger of frost is gone, and your soil's warmed up to at least 60°F (15°C), plant them deeply, burying a bit of the stem; it helps them grow stronger roots. Give them plenty of space, maybe 2 feet (60cm) between plants. You'll need to stake or cage them early, these big boys get heavy.