Going to Magic mountain and Disneyland parks this October, would appreciate tips on how and where to get discounted 3 day parkhopper passes and fast passes.
Mousesavers (dot com) has a fairly comprehensive guide to getting discounted Disney tickets, as well as Magic Mountain tickets.
Remember if you are going in October that Magic Mountain has special Halloween activities. Disneyland does too and closes early some days. Check all of the schedules.
At Disneyland the decorations (and special ride overlays) start Sep. 14 and Mickey's Halloween party starts Sept. 28. This thread here has a ton of info and pictures on Halloween at Disneyland.
I don't know what date Knott's starts their Halloween activities.