How can I make my mixes sound finished

One of my favorite Dj's is 3LAU. He does these monthly mixes that sound awesome. It sounds like one big song.
Heres an example http://soundcloud.com/3lau/3lau-haus-22-march-mayhem?in=3lau/sets/3lau-haus
(I'm not sure how to link it)
I'm hoping someone can tell me what he does. Everywhere I look about finishing mixes they basically all have the same gist: All the songs are already done so you don't have to do much or even anything.

I don't believe that 3LAU has to do something to his mixes. He made a Tove Lo song that sounded like crap, sound like it was made yesterday. Can anyone tell me or guess how he gets his awesome finished sound on his mixes.

Hi JCop and welcome to Literecords!

Generally if doing a 'megamix' type mix using current (recent) tracks, you won't need to do a whole lot. Most current dance tracks have been mastered to give the same type of sound (big and loud), so will mix together fairly well without any noticable change in levels.
It sounds to me like this 3lau guy has done his mix, (adjusting the volume of each track he's used to get them all pretty much the same) then run the whole mix through something like Ozone mastering software to make everything loud and proud.
Ozone is a great program as long as it's used in the correct way. Loads of big producers use it. Swedish House Mafia used the s**t out of it on a lot of their stuff.

I hope this helps somewhat.... or I might be totally wrong in which case.... ignore all the above!

It's all about your master bus. I agree to Pablo, Izotope Ozone is a powerful mastering tool if you use it right. Even choosing a preset can sometimes improve your results and give you a louder and wider master mix.

Watch the DB's, and learn how to use a limiter / compression. Nothing else is needed as the tracks are already finished articles.