I prefer to have the genuine article or scans to base what equals a "correct" tag off of.
I don't fuck with MusicBrainz or anything like that... I just reference the artwork and use exact names (correct tagging and aesthetically-pleasing tagging do not mean the same thing... if "(Feat. so-and-so)" is the title, then I keep it (unless it is clearly written as a form of subtext in a clearly smaller typeface, denoting it is additional info as opposed to a part of the title).
My biggest sin is Having Each First Letter Of Each Word Capitalized (same as Discogs rules, but I've always done titles that way, so the compulsion comes naturally)...
I do this even if it's a word like "and" (and always use "&" if the tracklisting/band/album uses an ampersand instead of the actual word). I am also very particular about true-to-title use of punctuation marks.
I only do AbnORmaL or ALL caps if it's clear this is the intended spelling (like, if a song in a tracklist is the only one with said abnormal capitalization, as oppose to being done for aesthetic reasons).
I fucking hate when stuff is mis-tagged, especially stuff I have scrobbled 54525242524524 times before noticing. I check that shit obsessively now, especially since I lost scrobbles deleting a bunch of shit because some fucktard always puts "EP" at the end of a release title.
Genius, I know it's an EP... That ain't in the NAME of the fucking release though (I realize some EP's actually do have it in the title, but many that don't still get tagged "_________ [EP]", which drives me up the wall..
For my own vinyl/CD rips, I keep the tags immaculate and true to the release, referencing them directly, or using scans/Discogs tracklistings (not always correct, BTW) when it's a downloaded release.
As for splits, I keep it simple: if it's two bands with no obvious shared titled, I just name it "______/______" in the album field. Otherwise, I only use the A-side title if a split's B-side is left untitled... which is totally wrong, but.... it's sometimes kind of a grey area of uncertainty with some split releases... and sometimes they are marketed this way when purchased (perfect example being the "Maggots" split with NunSlaughter and Mutilated Messiah, the later who are on the B-side and have no title for their half of the split, though NS do in fact have a track called "Maggots" on their side as the opener... and everywhee you look, it's referred to simply as the NunSlaughter/Mutilated Messiah "Maggots" split.