I am a FTM and by no means an expert, but here is how my EPing has worked out.
I started to EP when LO was 2 weeks old. (She is now 13 weeks) My initial pumps were maybe about a half ounce a side every 2 hours. I would pump a minimum of 15-20 minutes and try to let the pump go for an extra five minutes after the milk had stopped coming out to try to signal my body to make more. In the first 2 weeks or so of EP'ing I pumped every 2 hours during the day and every 3 at night (from 10 PM to 6 AM or so). I would also pump one side at a time because I read that is more similar to what the baby does and is more likely to trigger your body to produce more milk.
The first jump I saw was when I went up a size in the breast shield. (I have a Medela pump so I went from M to L) That instantly got me an extra ounce or so on each side. The L was still chafing me, so I went to the XL and that got even more milk out. After those first 2 weeks I was able to go about every 3 hours during the day and get up twice at night to pump. I stuck to the 15-20 minutes minimum a side with letting the pump keep going after the milk had stopped to try to help build my supply.
Since DD was about 9 weeks old, I get anywhere from 22-30 ounces in a day. I went back to work when she was 10 weeks old so I'm now pumping 5 times a day during the week. (Once before work, twice at work and then twice more at home after work). The first pump in the morning and the 2 pumps at work tend to be about 30 minutes a side. (I had to stop double pumping because I was getting clogged ducts...probably because I wasn't draining myself enough trying to do both sides at once) The last 2 pumps of the day are back in that 15-20 minutes a side range. I try to pump more frequently on the weekends to keep my supply up and to prevent the clogged ducts.
I added the all extra info just because it is HARD to EP and building a supply takes a lot of work. I was really discouraged to get so little in the beginning, but sticking with it has been worth it. We still need to supplement with formula, but not very much. Coming here everyday gave me a lot of great tips and advice and I probably would have given up if I hadn't had The Bump as a resource.
I also drink a TON of water and I use fenugreek (2 capsules twice a day).
Pretty much everything VIPRoss said in her first three paragraphs. I did almost exactly the same thing she did and ended up with great results and a pretty huge oversupply.
Re: EP-ers: how many oz