@Hylozoist Are you from the EU/UK? How is it over there?
I live in East London. It's chilly, and it's probably going to be a pretty nippy weekend as well. I'm guessing you don't mean to ask how the weather is, so let me give you my Really Quick Rundown Of London.
It's busy. It's expensive. There is nearly always something going on if you want to do something. Get familiar with how public transport works. In that way, it's probably like most other cities. I like to think that we're all very polite and tolerant folk, but a great deal of that is probably due to nearly everyone here never really talking to one another. In fact, that'd be the first rule I'd want to impart on you for a visit to London; don't try and strike up a conversation with somebody on public transport.
I say this only because there's always at least one tourist who breaks this rule on any given tube journey. I've seen it happen. The look of panic in the eyes of the person who is being spoken to, the shocked looks of everyone else, it's awkward and uncomfortable and God help you if you do it, because nobody else on that tube carriage is going to help you.
Some places in London are pretty rough. I assume this is the same for most cities too, really.