Groove! Groove! Groove!
What is the most important aspect of a song? Of course, the story it tells. Why are there still arrangers who just write something without understanding this? Based on the meaning of the song you make the choice for the groove of your arrangement. Do you commit to the original groove of the song or you have another cool groove in mind to give an interesting twist to your arrangement? It does not matter what you do, as long as you make up your mind.
Yet I still hear a lot of arrangements in which either there hasn’t been made a clear choice for a groove or that the it just isn’t right. This is often because they are unaware of the groove of a song.
There is a lot of information to be found on the internet about grooves. Just start your search by taking a look at this article on Wikipedia. From there you can proceed your search at the bottom left of that page. It is also helpful to learn about grooves for drums and percussion.
Learn to analyze grooves by listening to the bass and drums. Then 50% of your groove will already be clear. Would you want to write something totally different than the original groove? Make sure you write clearly your bass and drums (also in a cappella).
Whatever you do: MAKE UP YOUR MIND! If you have made up your mind for your groove your arrangement will be more consistent.