A very easy and simple method is to introduce the branch or leaf or so (with full of feeding adults and nymphs of aphids) in to a conical flask (see that it is fixed to a holder).Cover the mouth of the flask with muslin cloth keeping the branch or leaf with minimum disturbance while securing.
Introduce the branch of potted plant with full of aphids infestation into the conical flask.Tie the flask with a stand. Cover the mouth of the flask.Leave it for two days. Honey dews are collected at the bottom of the flask.