ABC analysis
A technique that has been used in business management for a long time is the categorization of large data into groups. These groups are often marked A, B, and C—hence the name. Activities that are perceived as having highest priority are assigned an A, those with lowest priority are labeled C. ABC analysis can incorporate more than three groups. ABC analysis is frequently combined with Pareto analysis.

Pareto analysis
This is the idea that 80% of tasks can be completed in 20% of the disposable time. The remaining 20% of tasks will take up 80% of the time. This principle is used to sort tasks into two parts. According to this form of Pareto analysis it is recommended that tasks that fall into the first category be assigned a higher priority.

The 80-20-rule can also be applied to increase productivity: it is assumed that 80% of the productivity can be achieved by doing 20% of the tasks. If productivity is the aim of time management, then these tasks should be prioritized higher.

Fit
The concept of fit is simple yet profound. Essentially, fit is the congruence of the requirements of a task (location, financial investment, time, etc.) with the available resources at the time. Often people are constrained by externally controlled schedules, locations, etc., and "fit" allows us to maximize our productivity given those constraints. For example, if one encounters a gap of 15 minutes in their schedule, it is typically more efficient to complete a task that would require 15 minutes, than to complete a task that can be done in 5 minutes, or to start a task that would take 4 weeks. This concept also applies to time of the day: free time at 7am is probably less usefully applied to the goal of learning the drums, and more productively a time to read a book. Lastly, fit can be applied to location: free time at home would be used differently from free time at work, in town, etc.

 

Source : wikipedia.org