If you want to friend me, you don't have to ask. Anything I post online I consider fair game for everyone to see, so friend away.
I believe in anonymity on the internet, which is why I allow anonymous comments. If you don't like my fic, give me hell! I don't mind - honestly. I might reply and ask you to explain some more, but ultimately if I don't like your advice I just won't take it, so no harm done.
There's a lot running around, but I keep mine pretty basic.
NC-17: Penetrative intercourse, penetration w/ foreign objects (not inclusive of fingering) R: Fingering, coming w/o penetration, eg, blowjobs, handjobs, grinding, &c. Also, for extreme depictions of violence or swearing (though the swearing would have to be pretty extreme) PG-13: general in between: sexual innuendo, swearing, &c. PG: Would show my kids, though still might (probably) contain m/m relationships.
Due to the fact that my rating system is pretty cut-and-dry, I don't give warnings for "m/m sex" or anything like that. The theory is that 1.] If it's NC-17, there's sex, you don't need to learn that in the warning as well, and 2.] It's offensive and homophobic to warn for m/m sex when you wouldn't for m/f sex.
Warnings in general are things like: bondage, dub/con (dubious consent), gunplay, rimming, DP (double penetration), roughplay, &c. Stuff that's a little more kinky, and might be something that someone doesn't want to read.
Avengers - Tony/Steve, Coulson/Clint The Walking Dead - Carol/Daryl Tolkein - Legolas/Gimli, Fili+Kili