The first number on the bag tells you how much nitrogen is in the mix. Many say this is the most important ingredient in fertilizer. It helps the lawn stay green.
The second number on the bag represents the amount of phosphorus. It strengthens the roots of the grass.
The third number stands for the amount of potassium in the fertilizer. It helps fight off diseases and helps grass survive hot dry spells.
Pay attention to the type of fertilizer you buy. Quick release fertilizer is soaked up by your lawn right away. Many turf pros recommend slow release fertilizer. It provides a consistent feeding to your lawn.
Types of Spreaders:
Hand spreader – good for small areas
Drop spreader – works well near flower beds, drops fertilizer straight down
Cyclone spreader – good for large areas, throws fertilizer out from underneath it
How to Fertilize Properly:
Adjust the setting on the spreader. Pour in half the bag of fertilizer and walk back and forth over your entire lawn. Make sure each pass slightly overlaps with the previous one.
Pour in the rest of the fertilizer. Apply the rest of fertilizer in a perpendicular pattern. Step on the turf and if the leaf blade bounces back up, your lawn is in good shape. If it lays flat, you’ve over-fertilized.
SOURCE:http://www.diynetwork.com/how-to/outdoors/gardening/fertilizer-tips