Before you begin putting big band charts together, I would highly recommend becoming very proficient at writing charts for smaller groups, those that consist of 3-5 horn players. Why? Because writing for these types of groups will really ingrain some basic fundamentals that you can then carry over into your big band writing.
Remember that when “voicing” a chord for any group of instruments, you should strive to have the chord sound good strictly on its own. In other words, your voicing should reflect the harmony as best as it can.
Keep in mind that a big band is really made up of smaller groups – “sections” of 4 and 5 players. These sections can (and should) be thought of as being able to “cross” each other. For example, you could have a part (or parts) of a big band chart that consists of a 4 horn ensemble within the big band. So becoming skilled at writing for smaller groups helps you with arranging for both small and large groups.
The following video gives you some ideas on how to voice chords that include the upper extensions of the chord in the melody notes. If you have questions or comments, please leave them below the video. I have included a sample sheet that includes more voicings, and a few practice voicings you can fill in yourself.