• Don't mow in early spring - the dandelions and early flowers are some of the seasons first nectar sources
• Wait longer in between mowing
• Leave areas (or all!) of your yard that you don't mow at all
• Add a few rocks to your birdbath so they can access the water easier

Plant pollinator friendly trees and plants helpful links:

• The Biota of North America Program
  
• Penn State Extension - Planting for Pollinators
• Penn State Extension - Best Plants for Pollinators
• Rutgers - Blooms for Bees: How to Provide Pollen and Nectar Sources

• US Fish and Wildlife Service - How You Can Help Pollinators
• Penn State Extension - Pollination and Bees
  
• Penn State College of Ag Sci - Center for Pollinator Research
  

• Xerces Society for Invertebrate Conservation