Organize your Work Area
Having your supplies and tools accessible will improve your efficiency when working on a project. By cutting down on the time spent looking for things you need, you put more time back into your construction.
Invest in Tools
Having the right tools is important not just for the quality of your costume, but also the speed at which you finish it. If you find yourself routinely making bias tape or ruffles, having tools such as a ruffler foot or a bias tape maker will improve your workflow. Owning rotary cutters can speed up cutting out patterns.
Take short breaks regularly while working. This will help you avoid burn out and improve focus. (Just don't take a break doing something that is a time sink!) Give yourself 10 minutes every so often to disconnect from your project. You'll produce better results by avoiding overworking.
Calendar Out Projects
Using a monthly calendar to chart out deadlines for costumes will allow you to visualize just how much work needs to be done. It also can help you rationalize a realistic timeframe for making something. Writing out notes and estimates on how long you think you need to complete a project will help you make better choices on how many costumes you obligate yourself into to making.
Use Apps that Help with Planning
There are a number of organizational applications available for smart phones, computers and tablets. Making use of calendars, project planners, and list applications can help you stay on track. The application Cosplanner is one app that is geared towards cosplayers specifically, and contains a number of features that are extremely useful.
Be honest with yourself about what projects are more important to you. Taking on too many costume plans can sabotage all your projects. Many cosplayers will opt into making too many costumes and end up not finishing or not being satisfied with what they make. It is important to consider what projects matter more to you, or you may bite off more than you can chew.
Outline your Goals
Avoid Time Sinks
Best of luck on your projects! <3