Three important tips for applying beneficial insects in your garden

1. Release the correct beneficial – the pest in question needs to be identified first before choosing an appropriate beneficial insect.
2. Ensure proper timing of release. it is just not enough to release a beneficial hoping they’ll stick around ‘just in case’ a pest shows up;  the timing of release must coincide with pest emergence
3. Provide a favorable habitat to establish a permanent presence in the garden. Beneficial insects need more than just the pest as a food source;  they also need refuge, nectar, pollen and a water source. As the Lawn Blog says: “Luckily, attracting beneficial insects is easy.  Provide a habitat they’ll like, avoid using chemical pesticides and attract and keep them around with all-natural, easy-to-use products.”

Related Info: http://www.thelawnblog.com/2010/03/03/attract-beneficial-insects-for-all-natural-pest-control-and-greater-yields/