Ride the train; beware of robbers.
Ride the Stagecoach.
The bumper cars are not too slow for 10-year-olds and their parents.
In my opinion, Mystery Lodge has aged surprisingly well.
If it's hot and you see the western stunt show in the outdoor theatre, sit in a covered wagon or--if they're full--sit in the spash area near the stage.
See the saloon show in the summer. They have two funny can-can dancers in the show during the summer that might make you miss Disney's pre-Eisner Golden and Diamond Horseshoe Revues.
Jaguar is a great, first, big coaster for kids.
Xcelerator is a nice, last, big coaster for aging adults.
Bring some frozen water bottles because beverages are even more expensive than they are at our beloved Disneyland. Employees are very nice about giving free glasses of ice water at refreshment windows.
Ride the Pony Express first and if no crowd is there yet and the employees will let you stay on, ride it around twice. (It's so short, it should take everyone around twice--then it's a worthwhile ride--at least for me and my kid.)
Knott's Season Pass might be the best theme park deal in S. Cal. For about $100 more, one adult can purchase a Platinum Pass that includes parking. Both the platinum and Gold passes include the adjacent Soak City water park. How does this compare with Raging Waters? Any tips on how to enjoy this water park? The Platinum Pass also includes admission to all Cedar Fair parks in 2014, including Great America in Santa Clara--south of San Francisco--and the great Cedar Point, which is like Magic Mountain, but is more scenic (along Lake Erie in Northern Ohio), and with--in my opinion--better roller coasters. The Gold Pass also includes admission to Soak City.
Season passes don't include the phenomonal, transcendent Halloween Scary Farm , which you must experience. (Visit that in late Sept. for shorter lines and fresher monsters.) The Hanging is an insightful chronicle of our times; stand in the "slash area" near the stage. I suggest that you NOT bring kids under 13 to Knott's Scary Farm.
Return for Christmas (no separate admission unlike Disneyland's special Halloween and Christmas parties) and enjoy the small stage shows in Birdcage Theater. Snoopy on Ice shows range from good to excellent. My daughter enjoyed the Christmas parade where guest kid marchers (who'd rehearsed) added a charming small town-like feel, but Gerald70, in a post below, wrote that the Christmas parades were discontinued in 2013. Thanks, Gerald.
And thank you, Miceage, for your past lobbying for western music that better matched Knott's large Ghost Town!
Hope some of the tips are helpful!
Please add more.
Note: posts below made suggestions for changes to this list that have been made. Thanks again for those!