Well, if it's a new piece, before starting to practice it I first read it first sight as I can, slow, and I take this opportunity to check the fingering, or sometimes I'll just study the sheet music away from the piano and try to decipher the structure, learn the harmony and that stuff.
Next, I'll start to read again; if it's fairly easy, with both hands at the same time, if it's hard I'll start with one hand and then the other one. I'll take the first phrase and practice it changing the rhythm and with different attacks, let's say, 3 times 1 fast 1 slow, then 3 times 1 slow 1 fast, then 3 times 2 slow 2 fast, etc.
NOTE: It's important to be aware of a detail here, the purpose or repeating something is so that your body learns it, not for you to learn the music but for your hand to know the choreography, that's all; you're training your auto-pilot, and because of this it's important that you always repeat playing perfectly, you have permission to have just one mistake and on the beginning, repeat a mistake more than once and you're practicing the mistake, you must start over again. If you are going to repeat something, repeat it 100 times (100 is a metaphor, obviously) but 100 times PERFECT. Practice slow and gradually increase the speed.
Ok, after doing the above, I'll play the passage as it's written, slowly being completely aware of what every finger is doing, watching my position, my elbows, that I'm relaxed, wrist, shoulders, back, etc. Make sure the mechanics of my playing are perfect always, and repeat it that way until my body "thinks it was born that way"

. This will give me the tools and physical knowledge that will help me solve what's next, the music.
After learning it that way, my fingers most probably will know the piece by memory, so I just start working on the music, apply every thought I had about the work while I was analyzing it, think, wonder about ideas, try different approaches, find out what works, what's too corny, what's missing power, etc. And now I just make music

, or at least that's what I aim for. An idea.
So now I can resume it all to this: teach your body the movements, the positions, the choreography so that you dominate the piece and instrument so well that you can now comfortably transmit your ideas on the music.
PS and time, time doesn't exist while you practice, this might take you 1 hour, or 10 hours, it doesn't matter, the only thing that matters is the quality. Although, it's always better to have quality AND quantity
