Disneyland Resort will still be using it's 'legacy' paper ticket FastPass system in March when you plan to visit.
Only certain Attractions, typically the major ones, offer FP and to get one you cannot 'reserve ahead' as you may be used to now at WDW.
To obtain a FP, you must visit the one of the FP distribution machines of said Attraction.
These are typically located near the entrance to the rise you wish to experience in their own little area.
I'm sure you remember doing this in the past at WDW pre-2013.
Insert your barcoded Park ticket and collect your paper Pass.
You can then go off and do something else until it is time to return and ride.
Typically, you cannot get another FP for that Attraction, or any other within that specific Park until you reach the return time indicated on the paper Pass ...or two hours later, whichever comes first.
You CAN however hop over to California Adventure and get another FP to something in that specific Park.
At Disneyland Park, FP is availible for these Attractions -
Space Mountain
Indiana Jones Adventure
Splash Mountain
Big Thunder Mountain Railroad
Star Tours
Roger Rabbits' Car Toon Spin
Buzz Lightyears' Astro Blasters
Two other Attractions have FP, but rarely are they offered except on very busy days ( Autopia ) or for seasonal demand ( The Haunted Mansion during it's Halloween / Xmas overlay )
Over at California Adventure, same applies.....a select number of Attractions offer FP as well as the Park night time spectacle 'World of Color' and the 'Frozen' themed stage show.
You can get a FP to WOC' near the entrance to Grizzly River Rapids, and one for the 'Frozen' stage show near it's main entrance.
If you plan on seeing either Show, it is good to get a FP as it may increase your chances of getting a better spot to view the presentation.
What is also nice is that your Show FPs will not interfere with getting any other FPs that day...at either Park.
So it is possible to have three active FPs in your pocket between the two Parks on any given day!
It would be four if Disneyland Park was running it's nighttime show 'Fantasmic!' but alas it will not be running in March.
Attractions that have FP at California Adventure are -
California Screamin'
Radiator Springs Racers
Soarin' Around The World
Grizzly River Run
Goofy's Sky School
Hope this helps you out!