I'm a pretty open minded person, though in terms of the things I draw I'm actually quite strict... The following are things that I won't draw;
I do NOT take requests. I'll occasionally offer free pics to good friends, but that's it.
I don't take "suggestions" on what I should draw. Word it how you like, it's really just a request in disguise.
I only do art-trades with friends or people I feel I can trust.
I don't do fetish art. Don't care what fetish it is, I won't do it.
I don't do slash/crack pairings. It'd be wrong to make a gay character straight, so I see no reason that it should be any different the other way around.
I don't do yuri or yaoi art. I have no problem with homosexuality, it's just out of my personal comfort zone to draw.
As with my art, I'm pretty strict in who I watch. I watch people based on two things; their art and the person themselves. I GREATLY appreciate nice people. Too many times have I watched someone only to find out that they're the type to ignore any feedback or critique, which usually causes me to unwatch them. I don't care how talented or popular you are, I find it to be incredibly disrespectful. This doesn't necessarily mean I'll unwatch anyone simply for ignoring comments, however. If they come across as a genuinely kind person, then that's enough for me.
I try to respond to each and every comment I receive. I LOVE getting comments! However, there are a few types of comments that I will ignore. The comments I will ignore are;
One-word comments; "Nice", "Cool", "Sweet", "Cute", etc. If you aren't going to put any effort into leaving a comment, then I'm not going to put any effort into leaving a response.
Repeated comments; Leaving the same exact comment on multiple pictures. And changing one word doesn't make it a new comment.
"Creepy" comments; Trying to force me to be your friend, leaving "hey" or "hi" on my page over and over and over and over, etc.