Current DLR hotel discounts are "up to 30%" off. If you are unfortunate enough to be at a time of year when there is no "special" discount, there is always a 10% hotel discount with the AP. They do usually seem to be running some other promotion though as Hydroguy mentioned, and then you can expect savings of up to 25%-40% off depending on which DLR hotel you book and the time of year. Howard Johnson Anaheim on Harbor will also give you a 20% discount with a
Disneyland AP if you choose to spend some or all of your stay offsite. I have read also that the Anabella hotel offers a discount to DL AP holders, but I haven't personally used this one.
Currently, deluxe AP passholders receive a 10% discount at most restaurants inside the parks and resort hotels and DtD and a 10% discount off merchandise at most shopping locations in the parks and the World of Disney, Marceline's, Pin Trader's and a few other Disney owned locations in DtD. The merchandise discount is set to expire in January 2012. It has been extended several times over the last couple of years but still is not something to count on until Disney gives official word. Premium passholders receive 15% off at dining locations inside the parks and DLR hotels and 10% off at most restaurants in DtD. Premium passholders also currently receive 20% off merchandise purchases at Disney stores; this will revert to 10% off when the extra merchandise discount expires. Non-Disney DtD stores often extend special discounts, usually 10% off, to all AP holders.
Lego Store and Build a Bear are examples of such places.
You can book a hotel AP rate even before you purchase an AP online or otherwise. I agree that the trick is in finding out what the rates are. You would have to call. You can also watch the Disney website and take note if they are advertising big discounts. Also, while it seems the AP rate would be the best way to go, sometimes it's not. The one time we stayed at the DLH, I asked the phone rep to price things out both ways. As it turned out, we got a better rate with the special promotion they were running for the general public than we would have gotten had I just asked for the AP rate. So my advice would be to book your hotel before you buy an AP. You can still ask for AP rates and book using them and explain that you will be purchasing your AP upon arrival.
Your AP becomes active upon first park entry, not day of online purchase. Fortunately, as I mentioned, you don't need an active AP to book AP hotel rates. Unfortunately, I believe you do need an active AP to purchase tour tickets at discounted rates. There is an AP discount off the price of tour tickets. I haven't yet done a tour myself, but I thought you could purchase multiple tour tickets at a discount with one AP. You should call Disney directly and ask about the situation with a purchased but unactivated AP. I did read a thread elsewhere recently where somebody was able to purchase discounted Halloween party tickets with an unactivated AP by calling and talking to a CM directly.
It is true that you cannot as an AP holder get discounts on regular DL park admission tickets.