What could I do to help outdoor gliders swing without squeaking?

In order for your outdoor glider to operate smoothly it is recommended that you apply joint lubricant to metal joints and bearings twice a year or seasonally as needed. For more information on care for your glider please refer to this website: http://www.doityourself.com/stry/how-to-care-for-your-porch-glider

Spray the hinges or areas that rub with WD-40. If that doesn't work, try coating the rubbing areas with wax, a wood floor wax should work fine.