Fortunately for everyone, and not just the basement-dwellers among us who are lacking in certain social graces, Pony society is not difficult to integrate into.
The 'Ponies' who live in Equestria don't call themselves such, and I only use that word here as a stand-in for the sake of convenience. Try not to let it affect how you perceive them. They are not 'animals' so refrain from talking to/about them as if they were.
Be aware of your size. It's embarrassing, and more importantly dangerous, given your weight, to trip over a local. If you need to talk to someone for more then a few sentences, it's considered polite to kneel down. If you won't be in the way of anyone, just sit. If you must stand, stand back far enough that you aren't looming over anyone. The laws of personal space still apply.
Ponies are very sociable. There are jerks and even the rare bigot, but they otherwise lack the comically overwrought social fears that humans have been piling up lately. Even in large cities, there is a certain small-town mentality. Everyone knows your name, no one freaks out when a stranger talks to a child, and few doors are locked at night. Most doors don't even have locks. This doesn't mean that certain limits aren't in place. Just as in human society, certain behaviors are socially unacceptable. Just because they walk around naked doesn't mean you should stare. Or that you are free to follow their example. Please, just keep the damn pants on.
Ponies are pretty mellow, and you should find fitting in not much harder then if you traveled to a different country on Earth. It's just a matter of watching, getting involved, and learning the unwritten rules.
That being said…
Human brains are incredibly complex things, wired for empathy towards other humans through a range of inbuilt instincts. Consciously or not, we recognise the shape of a human face, find ourselves reacting to body language, and pick up the subtle chemical cues given off by others.
But in Equestria, Humans are not the sole sapient species. The simple Human/not Human distinction we grew up with begins to distort. You can expect to meet Ponies, Griffons, Dragons, and a great many others who all meet the criteria of 'person' rather then 'animal.' A final layer of confusion is added by the resemblance of various locals to certain terrestrial animal species, which is guaranteed to mess with your head in ways you can't yet imagine.
You may find yourself retreating into old patterns of behavior by speaking to and handling them as you would a pet. Or you may get along so well you find yourself inexplicably attracted to a local. It's an awkward process that we all go through sooner or later. How you choose to deal with it is entirely up to you, and Equestrian society thankfully expects little more then simple politeness in your dealings with others.
And I really wish you freaks would stop asking…
Yes, inter-species relationships do happen. They are extremely rare, and while they do not suffer from any great stigma, neither are they particularly well-received. Just as humans were built to be, 99% of Ponies will only ever be sexually attracted to another pony. In the majority of cases, this means that when a Pony from that 1% grew attached to someone, that someone was most likely a member of their own species' 99% and incapable of returning such affection. A handful of such famous stories have been immortalized in literature as romantic tragedies.
And if you are one of those exceptions, and you find someone capable of accepting you…
Despite what some rather embarrassing rumors floating around may say, I cannot offer any great advice on this subject. Pursuing such a thing is an extremely personal choice for all involved. Expect a great many unknowable hurdles before you, as these relationship are such rare occurrences. I can only suggest that you pursue the matter with great care and patience.