[the following is a modified repost from PhotoSynthesis, 2009]

Step 1. Locate a suitable patch of forest, field, or desert.

Step 2. Wait for a warm, moonless summer night.

Step 3. Using a long extension cord, plug in a blacklight. Or even better, a mercury-vapor lamp.

Step 4. Sit back and watch your prey arrive.*

*disclaimer. This technique works generally for most entomologists, but if your needs are more specific, you will wish to employ more specialized methods. Forensic entomologists prefer roadkill, for example.