At the end of the Dragon Ball series we can see Goku fly off with Uub towards his village to train. There had been years of peace so we see Goten and Trunks all grown to teenagers, yet in the Super series they are still young. So it seems that Uub does not exist yet and the Super series does not follow directly after the Dragon Ball series, the same way the GT series did. So where does it fit in? When does the Super series take place?
In the last episodes of Dragon Ball Z, the Tenkaichi Tournament takes place 10 years after Buu's defeat.
Pan is one of the tournament participants, at the age of 4.
Goten and Trunks are teenagers.
In Dragon Ball Super, Pan is still in Videl's womb.
Trunks and Goten are still kids.
You can say that Dragon Ball Super takes place before that tournament and after Buu's defeat.
Mind-blowing fact: Goku can already transform into SSG in that same tournament eheheh :D
EDIT: Here's the timeline from the Wikia:
Dragon Ball Super
Around August 18 Beerus awakens from a slumber and searches the Super Saiyan God.
Bulma's birthday party is held on a cruise ship.
Dragon Ball Z
Age 781, May 7
The 27th World Martial Arts Tournament takes place. Mr. Satan wins. Buu comes in second place.