Sheds are considered as buildings and therefore should be built in compliance with your local building codes and permits. Check all your local codes and utility plans. It is prohibited to build your shed over existing water, phone, gas or electric lines as they should be easily accessed for maintenance.
The most common types of sheds are the gable shed and the gambrel shed with loft. They are easily built using materials from your local DIY stores. Hiring a team of professional will make the job done faster, but if you have a lot of free time it is possible to do it alone and greatly cut the expenses. Check those 2 plans and build a perfect storage for your garden tools and other goods yourself!
How to Build a Gable Shed Free Plan
How to Build a Gambrel Shed Free Plan