I think first it is important to understand your goals. Is it just to shake a few pounds and get feeling trim and healthier? Or do you want to get in seriously good shape and are you ready to commit to it? Do you want to add muscle as you lose weight, or increase your cardio, is one more important then the other?

There are some obvious answers to your questions, but they might end up kinda vague unless you define your goals. As in, how often are you willing to work out a week?

If you take a look through some of the training logs that will give you an idea as to some of the routines we are working. I know Salty has his in his blog and it is well-defined.

What do you have access to, for training other then an exercise ball?

I don`t really think the time of day matter so much, but how you approach the workouts before and after them, both in eating and preparation. Plus the frequency and intensity.

Everyone should be drinking about 3-4 liters of water a day, for starters.