Er, why is Debian your choice? My personal recommendation is Manjaro, it's based on Arch Linux which is my personal favorite flavor of Linux and it comes ready-to-play. Debian is still easier than, say, Gentoo to install but it's going to be a more difficult user experience.
Arch is basically the OS that makes you do literally everything.
This is good and bad for what should be fairly obvious reasons.
I'm not familiar with Manjaro, but it looks more user friendly.
If you want a really user friendly OS, go with Ubuntu. I don't recommend it for anything other than that though - I'm running Debian and Crunchbang myself, simply because they're so much lighter weight than Ubuntu.
Another thing to note is that Arch uses different utilities than Debian - specifically the package manager. On the other hand, they're pretty much the same, just some minor syntax differences.
I personally think Debian is more "straight forward" than Arch, but I've literally never used Arch, so yeah.
Okay. So before I actually dual boot this stuff I wanna try it out first. Is there anything I need to know before installing Debian on a VM?
Nah. Download it and slap it on a VM. Try to use it for some dev work or whatever. Then try a live boot and take advantage of the spare resources.
I just chose it because it said that it was the most basic one you could get. I tried ubuntu and disliked it greatly, so I wanted lighter. I'll give Manjaro a shot first I suppose.
Debian is lighter than Ubuntu by far. What didn't you like about Ubuntu?