As a player of multiple infamous evils, most notably Ilye Sena and Jalil, I figured I would add my two cents on this.
First of all, I agree that yes, sneaky evils are probably better recieved than blatent evils, but I get the general feeling that the opinion is blatent evil shouldn't be played, and that I have to disagree with. Blatent evils are alot harder to play than sneaky, covert evils in their own way because they are not as well recieved and sociable as covert evils, but they can be good characters when properly played. Agreed that when you have a dozen new "I'm the baddest thing in the universe" evils every few days, it starts to get old, but when you get just one blatantly evil person who people can gather together and hate, it can be alot of fun, and bring alot of excitment.
For example, if anyone does remember Sena, she was very blatently and unashamedly evil. One of the best examples of this was the cruel games she played by taunting the friends of her torture victims by delivering pieces of the victims to their friends, or by wearing trophies of her past atrocities, such as when she took the wings from a young gold dragon and had them grafted to her back, or her wearing the stolen amulet she took and twisted with dark magic when she killed Bhryn one time.
Of course, this
should not be the only kind of evil. Evil is more than just cruelty and malice and downright not giving a damn about the well being of others. It's more than
just being "in your face". It's that creepy feeling that crawls across your skin leaving a trail of goosebumps after a conniver has turned the tables and landed the good paladin in jail for a crime every believes he couldn't possibly have commited...or the realization that you've been duped by the fiend from the pits and just traded away your soul in a binding bargain, or the frustration of knowing that you can't do anything about the murder you witnessed becasue the murderer has blackmail that would ruin your life.
This too is evil, and can be just as, or sometimes more, exciting than blatent evil, however both are valid types of evil. The key is in playing them well. I look back on Sena and see so many things I wish I'd done differently in playing her, but on the flip side I see all the fun that I and other patrons had, and in the end, that's what matters.
So, in closing, and to sum it all up, the keys to good evil, IMHO:
1. Be true to your character while considering others...unfortunate as it seems sometimes, this isn't a novel where we can decide for ourselves what happens to everyone else, but really it's all the better for it because that means ANYTHING can happen...and the possibilities are endless!
2. Keep an open mind, OOC. In my opinion this is one thing that's smothering the development of awesome storylines. Never deviate from your character, of course, but give something or someone new a chance before labelling them/it. Just because your past expirience with evil has been bad doesn't mean every expirience will be so. It just takes finding that right kind of antagonist for your character that has the ability to send chills up your spine after a good confrontation...and it tends to send chills up your spine when it's right

3. Have your limits. EVERY great evil has their flaws and drawbacks. One of Sena's was her sister, Cena, whom she had dragged along with her to join the Shadows, eventually leading to her sister's complete insanity. I think it's key to have flaws and imperfections in a character...it's what makes them unique! And in the case of an evil character with the right role-players it can make the interaction that much more interesting.
Eh...I think that's all for now...please take it in stride. There have been some very good points made here in this topic and I hope people will take them to heart before they set out to play an evil character.
*drops in the two coppers and presses the big red button to post*
~Draggy