La Guardia Airport is so close that you can walk your way.
If you arrive at the main terminal, follow the cars exiting over the bridge that crosses the Grand Central Parkway. On the bridge you are in 94th Street. Turn right to Ditmars Boulevard. You will pass the Academy of Aeronautics on you left. After that building, Ditmars joins 23rd Avenue. At the corner of 23rd Avenue and 85th Street, there is park that start a series of small parks that you can use to traverse from the corner of 85th Street and 23rd Avenue to 78th Street at the middle of 30th Avenue and 31st Avenue. From there you turn into 78st and walk to the for corner with 34th Avenue. The walk should take no longer than one hour.
If you arrive at the east end of the terminal, you can take 102nd Street to cross over Grand Central Parkway. You are then at a large round-about. Pick 23rd Avenue and follow all the way to the corner of 85th Street. You meet the series of parks and follow the instructions in the previous paragraph.
If you arrive at the Delta Shuttle, you exit the airport and turn left into 82nd Street. After crossing Astoria Boulevard, you can see the series of parks at your right. Enter there and navigate diagonally to 78 Street. Follow instructions as in the first paragraph.
If you must use public transport, have change ready. Board the Q33 bus. It will make its way to 82nd Street. After it crosses Northern Boulevard, get off. Look for 34th Avenue. Walk down 34th Avenue to 78th Street. You will find my building at the far corner.