1. Yes, you can mix urine with juice. I believe it does decrease its efficacy, but if that's what it takes for you to drink it, then by all means.... A lot of people mix it with orange or apple juice. Others use juice as chasers and drink their urine straight up.
2. Yes, you can drink it diluted with water. If you dilute it 1:1, that's not homeopathic solution. Diluting it about 10x would make it homeopathic. In higher dilution, drop it under your tongue and leave it there for several minutes.
3. The smell of your urine is directly related to your food intake. If your food intake is less than "pristine", then your urine will reflect it. If your diet consists of solely raw fruits, then your urine will become clear with a subtle flavor of the fruit.
The more you drink your urine, the more you will be intuitively directed towards the proper types of food to consume.
And the only thing you have to lose is your own ego.