At the most I get 2-3, so my tactics may differ. If you have more, it best to drop them in a spread to prevent enemy movement, but still keep them close to eachother.
Most often I either drop em early to get the most use out of them.
They work well either by entering behind enemy lines and taking commanders/artillery out, or landing on objective hexes or bridge to prevent early capture.
Sometimes I keep them back to face a threat the enemy has (Armored cars or apposing Paras/Heros. But for the most part they pop out pretty early! :D