Determinate tomatoes need minimal pruning-- just prune off any suckers below the first set of flowers! That's all you need to do.
Do the same for indeterminate tomatoes-- but keep pruning off any new suckers above the first set of flowers.
On indeterminate tomatoes, new suckers will turn into new leader stems. By pruning off all new suckers, you'll be left with one leader stem that's easy to stake!
Once your indeterminate tomato has 3-5 tresses of fruit, pinch out the top to stop it growing taller. This will send more energy into developing tomatoes.
Some branches only produce leaves. These create energy for the plant, so it's important not to prune them.
for the full guide and more info on when & how to prune tomatoes