If you are planting outside in the ground you must plant in a completely different area each year and always destroy the tomato plants after they have finished fruiting - so not compost even if they are not blighted. Blight spores can live in the soil for years so do not plant tomatoes or other solanum such as potatoes in the same place for 7 years.

If they are in a greenhouse you need to dispose of not just the plants but the actual growing medium I'd also give the greenhouse a through clean to ensure there are no remaining spores.