When I first got Lady I took 3 weeks off to be with her, then came home at lunch until she was about 6 months old. I used to crate them but leaving them alone all day I didn't feel this was the best option. Lady now gets the kitchen with a bed and some toys, and Gracie gets run of the apartment. I am gone 5 days a week for about 7-8 hours. I walk them every morning and every evening. Personally, I think this situation is fine but I do not feel comfortable leaving them for more than 9 hours. I don't like to go out on work nights since they're home alone all day I like to spend as much time with them as possible when I'm not working.
I used to use the puppy pads but by the time they are around 5-6 months they can go the day without needing to pee. The only time they've ever had an accident is if they've been sick. If I had to work longer hours or had a long commute, I would hire someone to walk them in the day time but I think my current situation works just fine.
Read the section on preparing for your puppy, there is really good advice on how to set up a pen-area for your puppy so they can't get into anything. Like I said, I use my kitchen and have a baby gate so she can't get out. Also, doggy daycare is a good option too if you can afford it and if there is a good one in your area.
Lady (1.5 year old tricolour) & Gracie (4 year old blenheim)
"Happiness is a warm puppy" - Charles M. Schulz