It's so freakin' simple!

[Kawaii Ryûkishi]

Team names. Are singular. One team. Not two. Not 50. One. Chelsea <b>is</b> good. Not are. IS.

It can go either way when you're referring to a collective. Square makes crap games. Square make crap games.

One thing that bugs me about this is when people just add an apostrophe after someone's name that ends with an "s"(i.e., Bleys' Crotch), which is not correct(it's "Bleys's Crotch). You only add the apostrophe after a plural noun.

Again, either way is correct. I always add the S, though.

This bugs me, because it sounds wrong, but "data" is its own plural.

I thought data was the plural of datum.

It's both the plural form of datum and a mass noun like "information." Also, for the record, I hate every single one of you bastards who say "forums" instead of fora.

and people using he/she annoys me. Even if 'they' isn't terribly correct, it still flows better^_^

"They" is incorrect, and "he/she" is unnecessary. When speaking in general terms, masculine pronouns cover both genders.