Hi Robert,
Welcome to the forums!
You have received excellent tips above. For ease of navigation, I will provide some of the links where you can find all the guides.
The first days, it's mostly about getting the pup used to his new place and the crate and starting potty training. Puppy may whine at night so keeping him in the bedroom with the crate nearby can help him habituate and can help determine when and how often to be taken out (2-3 trips at night/early morning are not unusual initially.)
Love the crate exercises:
https://www.braintraining4dogs.com/members/video-archive/love-the-crate/
Main article on potty training:
https://www.braintraining4dogs.com/members/archive/7-secret-potty-training-strategies/
Advanced potty training program:
https://www.braintraining4dogs.com/members/advanced-potty-training/
Obedience guides are found in the link below. Since your dog is likely a young puppy you will need to factor in short attention spans, so make those training sessions brief and fun (you can start with just 2-3 minute sessions spread in 4-5 sessions throughout the day and see how it goes.) You want to end the sessions with your puppy still having fun so to inculcate eagerness to being trained.
https://www.braintraining4dogs.com/members/brain-training/obedience-101/
Importance of socialization:
https://www.braintraining4dogs.com/members/archive/socializing-your-puppy/
Smacking sound:
https://www.braintraining4dogs.com/the-airplane-game/the-smacking-sound/
Handling exercises:
https://www.braintraining4dogs.com/members/archive/exercises-to-teach-puppies-to-tolerate-touch/
Bite inhibition and bite inhibition games:
https://www.braintraining4dogs.com/members/archive/biting-mouthing-nipping/
https://www.braintraining4dogs.com/members/archive/bite-inhibition-games/
https://www.braintraining4dogs.com/members/archive/train-dog-take-treats-gently/
Prevention of resource guarding:
https://www.braintraining4dogs.com/members/archive/the-importance-of-preventing-resource-guarding-in-puppies/
Brain games are great to keep your pup busy and mentally stimulated:
https://www.braintraining4dogs.com/members/brain-training/
As your puppy develops, exercises to prevent separation anxiety:
https://www.braintraining4dogs.com/members/archive/exercises-to-prevent-separation-anxiety-in-puppies/
With a large breed dog as a mastiff, tackling jumping early is important:
https://www.braintraining4dogs.com/members/behavior-training/jumping/
If you search the forums you will also find loads of extra tips for puppy nipping and lots of other puppy related info.
Keep us posted when you get your pup!
Happy training!
Best,
Adrienne