Pot sizes, watering, and pest prevention

I'm going to be growing for the first time this season, and these are some really good seeds, so I wanna make them count. My first question is about pot sizes. How big should these pots be? From pictures I've seen, I figured a 15inch pot should be good for one plant, or maybe even two. Will I be able to grow two(or more) plants in one 15in pot? Also, I've heard that if you start a plant in the pot you plan to finish it in, it'll grow larger and healthier(as opposed to growing it in a small cup first, then a medium sized pot, then the ending pot) Apearantly, if a plant starts off in a large pot, the roots will grow deeper before they start to spread out, stabilizing the plant and giving it better access to water and nutrients.

My second question is about watering. How often should I do it? If this were in an indoor set up, I could check the soil for moisture content whenever I wanted, but this will be outside, where I have to be a bit more stealthy. I can't be going out every day to check the soil, I need to know how much to water in advance.

My final question is about keeping animals away. I won't really have this problem, but I'm still curious. I've heard that urine, human hair, and soap shavings will keep deer and other animals away. Is this true? If not, what will work?

 

Keep the soil moist but not wet, if you can.

The reason a single-pot plant grows larger (and not by much) is lack of transplant shock.

The container size becomes less relavant as control over other factors becomes more precise.

Good luck with deer. Some kind of noise-maker alarm works about as good as anything.