To get the greatest speeds from AirDrop it is usually best to disconnect from the wireless network and take advantage of the peer-to-peer nature of AirDrop.
This can be achieved by either deleting the network from Network Preferences, which is not convenient at all, or by using the airport utility.
Run this command to disconnect from the current wireless network:
sudo /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -z
This calls airport with the disassociate switch.
This is long to type so why not create a link:
sudo ln /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport /usr/local/bin/airport
Now the disconnect command becomes:
sudo airport -z
Now you can AirDrop to the max!