How Much and How Often to Water Plants?

I am having problems keeping my plants alive. Some are in pots and some I planted in the ground. I used Miracle Gro potting soil with all of them. How often should we water plants in this area, North Carolina?

The tomato plants turned yellow and then the leaves turned brown and shriveled up, but there were tomatoes on the plant. My hosta's leaves turned yellow and then brown as well. Some are doing great! They all came from Lowe's so I can get a refund, but I really just want them to grow. They are all about 6 weeks old here. Any advice?

By Amanda Carroll