One of the easiest ways to save money cruising is to maximize using your home port.

Living in Arizona, there are 2 cruise ports within driving distance. San Diego and Long Beach.
Most recently, we took a cruise from the port of Long Beach on Carnival Cruise Lines.
Let's compare driving versus flying for a family of 5
Our family of 5 for round trip flights was $225 each for our recent cruise from Phoenix (PHX) to Los Angeles (LAX).
Flights and Transfers:
Flights for family of 5: $225 x 5 = $1125
Carnival shuttle transfer $70 each ($35 per person each way)
Transfers for family of 5: $70 x 5 = $350
Total = $1475
Instead, we drove and parked our car on the Carnival offsite parking. You must park offsite on the 8 day sailings.
(*note this was required to be paid in full when we parked.)
Driving and Parking:
Carnival offsite parking = $180
Gas = $175
Hotel, the night before: $228
Total = $583
Some of you may say you could save on not staying in a hotel the night before, would be an additional savings, which is completely true but to save the peace of mind when traveling with a family of 5, including 2 teenagers.
Flying $1475 vs Driving $583
Savings of $892