My advise is to buy from the catalogs that are published here in the Northeast, as they not only offer seeds that grow successfully in climates similar to ours, but they tend to sell seed varieties that have the shortest maturing dates. In many instances, buying seeds that mature earlier in the season can make all the difference between success and failure. The next thing I look for in a seed is its resistance to disease. As you read through garden catalogs you will see letters lollowing the seed description that indicate its disease resistance. The same is true of seeds.
Resistance just means the seed has a stronger immunity to disease.
If you're like me, you have a tendency to go overboard when you buy your seeds. I think it is because the descriptions and color pictures, especially in January, conjure up pictures of fresh vegetables in July and August. If they are going to get too large for the area, I look for smaller, more compact varieties that will not turn my garden into a jungle I can't control. I have had success in carrying over favorite seeds from year to year. I place mine in the greenhouse.