I've had great luck with Bright Lances, Pulse Lasers, and the Fire Dragon tactic talked about above. Usually, I arm a Falcon with a Holo-Field and Spirit Stone, which makes them last nearly forever...even from a devastating Land Raider. They are the best tank in the whole game if you take these additions to the model. For weapons, I take Starcannons for Termies, or Bright Lances for vehicles. Load these up with Fire Dragons to deploy close and shoot up the tank, and you have a dead Land Raider. Even wiser....deploy the Dragons near a squad which is near the tank. Light up the squad for shooting, and have your tank do the same to get some extra kills in there, then have the Dragons assault the tank with their Melta-bombs.
One additional point to think of, and a tactic which has worked well for me, is to take your squads of Guardians and rush it up the field. You will lose some men (a given), but when you get to the tank, shoot anything around it, or Fleet of Foot to get closer, then swarm the tank, making sure to have men positioned around each of the doors. Use the Guardians haywire grenades to take the tank out, and once it is destroyed, any and all men inside the tank will die as well!!! With the doors all being blocked, nobody can escape the demolished vehicle!!!! What does this mean? It means that a single squad of Guardians are able to take out over 500 points of Marines easily, as long as the tank is transporting troops (especially Termies)!!! What a bargain!
Granted, it isn't easy to have your troops set up this way...but remember, Fleet of Foot can be a glorious battle winning tool if used correctly!!!!
Hope this helps you all!
One last point to remember: Marines are NOT able to mount troops inside a Land Raider before the game starts. It is NOT considered a troop transport like a Rhino is. It is able to hold troops, but they must be loaded into the empty tank after the game starts! This should help you all remember when the time is right for taking that Land Raider apart!!!