fastest if there's no traffic = taxi/Juno/Lyft/Uber
fastest if there's a lot of traffic and there's a well-timed LIRR train to Woodside = LIRR to Woodside, taxi/Juno/Lyft/Uber from there
fastest if there's a lot of traffic and there isn't a well-timed LIRR train to Woodside = E train to Jackson Heights, taxi/Juno/Lyft/Uber from there
almost as fast and cheapest = E to Jackson Heights, then Q70 to LGA (assuming going to terminals B,C,D--terminal A requires a different, slower bus)