Tongue pushing up. People might be getting confused because of the palatoglossus, the palatoglossus raises the back of the tongue. Second part of confusion might be the suction hold, you get a suction hold through a proper swallow, in a proper swallow you are eliminating the saliva on the roof of the mouth and getting the tongue to "stick" on the palate as well as pushing up.

Thanks, so just sticking the tongue to the roof of the mouth and relaxing the tongue muscles should be avoided? Because then the tongue would act like a suction cup and its weight would pull the maxilla downwards which we want to avoid?

@printfactor

I wouldn't worry about it, the suction hold isn't really that strong. If you want to get into proper tongue posture take a sip of water or use your own saliva and do a cheesy smile swallow, along with this correct your head posture. 

https://www.youtube.com/channel/UCfAFqPAZsa2TzzT8Ck-qAqg/videos

This channel/guy is a good source for posture videos.