Arranging a DJ mix is one of the core elements of creating a good set, and doing a good job makes all the difference in retaining engagement with your set. You might have selected some of the best tunes ever made, but if you don't put them together in the right order, you might not create the impact and excitement you want.
The underlying principles of effective DJ mix arrangment are: sculpting and maintaining energy, creating an attractive flow, buildups and breakdowns, harmonic mixing, phrasing, and contrast. It all depends on the context and environment in which the mix will be listened to. Also, consider how long you play a song - you don't want it to play for too long, but also don't cut it short!
DJ.Studio can make it easy to get an overview of the structure and arrangement of your mix.