Determine your needs. Small projects can be managed easily without specialized software, and the overhead of learning and using a new application can represent a net increase in overall work. Projects longer than a few months or with more than 100 tasks in their activity definition easily justify the use of at least a low-end project management tool. Considerations in selecting software include:
Cost (software, training, support, upgrades, or other expenses)
Adoption by peers (with resulting access to local expertise)
Ease of use (installation, learning curve, operation, updates)
Compatibility with organizational standards and related applications
Need for specialized risk analysis
Extensive resource analysis and tracking ...