There are times when you can tell a team is premade

The biggest tell is when your team spawns in like this: http://media.socastsrm.com/wordpress/wp-content/blogs.dir/173/files/2016/11/Black-Friday-GIF-2.gif

And they spawn in like: http://i2.kym-cdn.com/photos/images/original/000/983/772/318.gif http://68.media.tumblr.com/1ea5c4f55c96052ab5e50b562c9287a4/tumblr_nt1skkf85d1tdq4r6o1_500.gif