The Force.com platform supports attaching any number of triggers to an object, but there is no guaranteed order of execution, and multiple trigger instances often query the same set of data, which can cause performance and governor headaches.
To avoid these problems, and others, an accepted best practice is to delegate trigger handling to a second class, so that there is one trigger handler per object.
- A Simple Trigger Template for Salesforce
- Trigger Pattern for Tidy, Streamlined, Bulkified Triggers
- Advanced Apex Programming