Introduction

I have seen many junior developers having couple of Visual Studio instances running or one application running from build and debugging the other one. All that just because they had multiple applications in different projects and wanted to run them all at once.

Hey! Good news! You don`t have to do that!

Steps

1. Go to Solution Explorer, right-click on your solution and choose Set Startup Projects...
   
2. Select Multiple startup projects option and set Start action for each project that you want to start simultaneously
   
   NOTE: Order of projects on that list defines the order of their start.
3. After those two simple steps, you should be able to see Multiple Startup Projects option near Start button. Just hit start as usually all selected projects will run.
   
4. Example result
   

Summary

Quick and simple, but should be useful, if you didn`t know about it yet. Hope it helped!