Prepare for expensive vet led special diet and low exercise plan until adulthood, protect joints! Steep hills are a bad idea until fully grown.
Just train hard, cleverly and repetitively accepting nothing but total gentleness. Do yourself a big favour and ensure firm rules from the start so never on furniture, no food possessiveness, no face licking, no begging or treat feeding, never allowed to jump, made to lie down instead of lean, approach people to side instead of face on, humans through doorways before dogs, perfect heel and recall, sit at crossings, lie down if small animals/children approach etc. Head down is also a useful command because a Dane lying down can still hold head up at coffee table swiping height 
Your dog has to know it can't invade space and you have to teach that without using force because the dog is always going to outstrength you. Castrate as soon as possible. Halti works well for big dogs and horse lunge rope for recall training (because extending lead will break). Giant kong filled with frozen biscuit yuk for teething. Be warned though, don't leave alone too much as a pup, one of mine ate through a wall to find the mouse that lived there.
The hardest bit is socialisation and your best bet is to find someone with a pair of well behaved adult large breeds that can do that for you on a regular basis as part of your walk routine. I was lucky enough to find an understanding owner with a couple of big alsatians who sorted mine out (especially between 2-3 yrs when boundary testing is in full effect).
There is a firm rule about animal beds in our house. If the animal is overwhelmed then it can go to it's bed for peace and children are not allowed to disturb animals on beds. Everyone needs a time out space that can be respected!
I just made dog bed from duvet folded in half, if you are handy get 2 cheap fleece blankets from primark or ikea and sew together as a fluffy cover. Big dog beds a madly expensive and always need replacing on a regular basis so duvet is a much cheaper option.
Small dogs are often the worst behaved because they can be scooped up by their owners instead of trained as dogs should be. Big dogs don't have that luxury and need to be bomb proof.
Sorry this is such a long post, congrats on the cuteypup!