Each veggie type requires a different spacing when direct seeded into your garden so make sure to read the instructions on your seed packet before planting. Also make sure to familiarize yourself with the concept of "thinning" because about 14 days after you seed things like carrots and radishes in your garden you will need to thin them so that they can mature properly. Here is a helpful video on thinning.
As for the seed packets that we produce, the rule of direct seeding does not apply! There are planting instructions for each species in their item description.