Engineering in professional studios as well as my home studio I've had a lot of experience working with music artists. When sending your tracks online to get mixed it is very important to make sure that you send your songs the right way! This will save you and your engineer tons of time!
If you haven't already, I'd recommend that you watch the video on trackouts as well...
In this video I show you what trackouts are and why you should know! When getting your music mixed it will always sound better having your studio engineer mix your song with each vocal separate and each sound in the beat separate. That is how you give your song a professional mix. When buying beats online this is something that every artist should be aware of!
Some producers offer lease options with trackouts, others only offer trackouts with exclusive beats. Watch the video for a complete explanation on beat trackouts and their purpose.