Said that remember:
To put your fic on the net means you want someone to read it. If you don't want it to be read don't put it in the net but keep it in your desk table. To read a fic needs time. A person who does it doesn't get paid. He doesn't do it for having a better culture or a personal gain except to have some fun. So that's only natural and fair a reader could wish to give you his feedback. That's nice if you would answer to everyone who write you at least for thanking him/her. If you know you will never be able to answer to the readers' feedback it would be fair to warn them with a small disclaimer at the end of the fic. To write feedback means to spend time in the net and spending time in the net is hardly for free.
Feedback can be negative. Not all have to like your fic. It's only in your own maturity to accept it for improving your writing ability.
Sadly feedback can be stupid too. Many readers can disagree with what you wrote for reasons that aren't intelligent at all and you can be thankful when they at least choose to tell you their reasons. Sometime, sadly, they will choose to not even try to explain themselves. Be patient and choose how to act case by case. If someone is not agreeing with you, you can try explaining your point of view. If someone is flaming you just cause he/she thinks is vision of the world is the only one that deserves to exist is better if you ignore him/her. To argue with little children means only you're going to loose your time. You'll better wait they become mature and then talk with them. If they are too stubborn for understanding they are being childish or just plain annoying, well maybe you should inform them. Likely they will not stop but at least they will learn what it means to be criticized and that not all are willing to deal with babies.
If you're going to put in your fic contents that can be offensive or for mature audience (lemon, yaoi, yuri, violence, swearing) warn your readers. It avoid you flames from people who doesn't like that sort of things, problems with children who incidentally read it and it's only fair toward your readers. Besides doing it doesn't ask you a lot of time.
The most common language in the net is English. If you aren't English but you can/are able to translate in English your fic do it! You will surely have more readers and make happy people who can't read your language.
Long fics ask a lot of time for being ended. If you find out you have no free time anymore or wish to end it warn the readers and maybe give them a summary of how you were planning to end it. Remember is always annoying to spend hours reading a fic, wondering on his possible end paying daily visit to the web in which it's hosted and discover not only your curiosity will never be satiated but that the writer chose long ago to stop writing it.
Is someone asking you if he/she can put your fic on his/her page, use your characters or your situations or continue your fic? Well what does it cost answer yes? You too are using characters and situations who aren't completely yours (Studio Pierrot and WEP are the only ones who own SB and SRaTSS. Oh and yes maybe some companies who brought the rights from them. Everyone else who said the contrary is simply lying.) so you can't really blame someone who's homaging you admiring your work so much he/she wish to use it for creating another NOT PROFIT work. Just remember asking them to give credits to your work and maybe to put a link at it. Accepting can give life to new wonderful work, interesting cooperation and give you suggestions for your new works and info about how the readers see the world you created. If you really don't feel like seeing your work used by another person (it can happen and there's nothing wrong in it either) maybe it will be nice if you explain him/her. You have no reason to be offended so please don't be.

REMEMBER ALWAYS THE MOST IMPORTANT RULE:
Fans should be unite and don't argue for stupid reasons among themselves! We're sharing a passion, let's make it productive and pleasurable and not an excuse for starting battling between us!

Said that remember:
Before to read the fic read the warnings. If you don't want to read a fic with contents you don't like, aren't for your age, you think offensive read the warnings. If you don't do it you have only yourself to blame and surely not the author.
To write a fic means to spend time doing it. A lot of it. It isn't an easy work at all. All that many readers ask in exchange of sharing their intellectual work with you is to know your opinion about it. Let them know it!
Writers haven't necessary to share your ideas about how something have to be. To have a different vision of the world, to put together a different couple, to create a different future can't be blamed. You can, of course express your opinion, but remember 'different ideas' don't means 'bad fics'. Beside nobody force you to read fics you don't like. If you can't at all share the author's idea skip his/her works.
Write constructive feedback. It helps the author doing better works you will be able to read after. To write 'your fic is horrible' or 'I don't like what you write at all' means nothing. Explain your reasons or writers will think you have no reasons at all.
Hurting feedback or flaming feedback is the most stupid thing an intelligent being can do. Keep that in mind and prove your intelligence and maturity not doing it.
Not all the authors have the chance to answer at your feedback or to answer at it immediately. And not all the feedbacks arrives in the right mailbox... (Yep, that's true. I received a couple of mails that weren't directed to me... Remember always to type carefully the address!) If you don't receive an answer after many days and many tentative it could simply means the author can't answer at you. Don't take it as an offence. World is full of writers who're anxious to answer to your feedback.
As already mentioned to write a fic ask time. A LOT OF IT (as my Latin teacher would say 'repetita iuvant'... or something similar ^_^ In other words 'To repeat help'). Do not expect they will pop out of nowhere. What you read in half an hour can const days of work. Writers need time and inspiration for doing them. And sadly the time needed can be a lot. To write fics is not their paid work they have to deal with real life troubles as work, school, illness, home troubles, broken pc, other activities and yes, absences from home or holidays too. It's sad but this can means they have the right to make you wait a lot for reading another fic from them. And yes they can choose too to stop writing. In each moment of their life. You can be sorry, you can be desperate (in some cases I was) but don't blame them for that. As soon as you'll try to write a fic you'll understand what I mean.
A fic writer can make writing errors. Maybe more of what you can consider acceptable cause he/she could be writing in a language who isn't his/her own. If you want to be of some help instead of blaming the author tell him/her his/hers mistakes or the sentences you can't understand.
And, this should be obvious but there is still someone who forget it, no, you can't declare fics as yours when they're not or use them or the characters/situation inside them without the author's permission (and remember the author have the right to refuse his/her permission. He/she's not forced to say yes only cause you have all planned or whatever other reason...). They're his/her intellectual property from which he/she is not gaining money at all. Stealing them is rude, cruel, hurting, stupid and illegal so please don't.

REMEMBER ALWAYS THE MOST IMPORTANT RULE:
Fans should be unite and don't argue for stupid reasons among themselves! We're sharing a passion, let's make it productive and pleasurable and not an excuse for starting battling between us!