-Don't stay onsite. Not worth the $$$$ and unlike WDW, many of the hotels on Harbor are closer than the onsite hotels.
-Do at least 5 days so you can see most of both parks. While California Adventure can be done in about 1 - 1.5 days,
Disneyland needs at least 3 - 4 to see everything. Downtown Disney doesn't have anything that is must-do, so no need to devote very much time there.
-There are a lot of affordable hotels and motels directly across the street from Disneyland. I would choose one close to the Harbor crosswalk so you don't have to worry about catching transportation and can head back to the hotel whenever you want. We really like the Camelot Inn and Suites and Tropicana. You can get a pretty nice discount at both if you stay 5 or more nights. McDonald's is right next to Camelot, which is nice for a quick and cheap breakfast on the go.
-Definitely do rope-drop. This is when you'll hit the most rides.
-Reservations for dining aren't as necessary here. If you really want to do Blue Bayou, character dining, etc. it is a good idea to have a reservation but no need to book them too far in advanced.
-Disneyland uses the paper FPs, so no need to reserve those. Be sure to maximize them though. You can typically pull a FP every 2 hours.
-Get park hoppers so you can visit both parks whenever you want.
Edited to add: Fly into John Wayne Airport (SNA) if at all possible. LAX takes longer to get from. It's only about a 20 minute drive by taxi from the airport to Disneyland. Also, I would do a taxi rather than a shuttle service. It's a little more expensive, but you don't need to drop off other people and can get to the hotel quicker.