Personal relationships and privacy
Do not assume that you know everything there is to know about a writer simply because you read their weblog on a regular basis. Any judgements you make will be based on the information they have provided you about themselves, which is probably vague, incomplete or embellished. Whatever opinion you form on them as people, or their life as a whole, is probably best kept to yourself. Remember, you are the reader. An obvious exception to this would be if someone were asking for advice or opinions.
Never contact the writer for more details on events or personal information than what they have already provided on the site. Chances are if the information you seek isn't readily available, they have found it too personal or innapropriate to share. If you are close to the person they will eventually tell you privately, so intrusive questions are not necessary, just leave it alone. If you are meant to know, you will.
If you have a real life relationship with the writer, remember that communication is very important. View weblogs as online journals, no less sacred than a diary hidden between the mattresses. First of all let them know that you read their site, especially if they did not tell you personally.
If they do not want you reading it, or suddenly stop posting entries, ask them why and if necessary, stop going to the site. It is important that as a friend, relative, co-worker or whatever you may be to the writer, that your presence at their weblog not impede their ability to express themselves. Remember this is their outlet. They may not want you to read certain things they might write about you or others you care about, in order to spare your feelings, avoid drama or maintain their privacy. You should respect this and immediately stop going to the site, and never relay any information you gather at their site to others who might use it against them.
If someone writes about you and you don't appreciate it, approach them about it. Try to remain calm and polite. Explain that you are entitled to your privacy as well. There are many compromises that can be reached from using vague nicknames to protect your anonymity, or not mentioning you at all. If you are upset because they are writing negative things about you, be reasonable, try to see if there is a way to resolve the issues and mend your relationship with the writer. If that doesn't seem to be possible, stop going to the website. They will eventually get bored and move on.
Ex-friends, lovers and estranged family members who have been cut out of the writer's life should refrain from reading their journal. If the relationship has ended, there is no reason you should get daily updates on the person's life. If you simply can't help yourself, do it quietly, and never repeat what you read or use it to hurt the writer.
Feedback and initiating contact
If they have a guestbook, sign it. Compliments will always be graciously accepted and appreciated. Criticisms and reproaches are fine if you have a problem with something, but try to remain constructive and not be an asshole. No one is forcing you to give out your opinions, so if you don't have anything remotely positive to say, it may be best to keep quiet.
When contacting a person for the first time, have a clue. If they have a detailed biography and personal information that describes their life from the day they were born, chances are they won't appreciate you wasting their time asking them how old they are or where they live. Writers put a lot of thought and time into their sites, so take the time to read the information they provide you with before you ask for more.
Never assume a writer owes you any response. They may receive from a few to hundreds of messages per day. Some will gladly write back immediately, others will never reply. Try not to take it personally, because chances are it has more to do with their schedule than anything else. If you get upset and nasty about feeling rejected, you will probably ruin any chances you had of befriending the person.
Don't delude yourself into thinking that you will be as important to the writer as he/she is to you. Remember, you are peering in on their life, sharing their thoughts, and though they may become quite special to you, you remain a mystery to them. If they are cold or unreceptive to your advances, keep in mind that you are a stranger to them at this point, and they may or may not want to keep it that way. It's entirely their choice.
Don't be a psycho stalker.
You shouldn't contact people with messenger services unless they list their handles on their website. If you got it from someone else, forget you ever had it, they probably meant to keep it somewhat private.
A writer has the right to stop writing at any time for any reason they see fit, and at no point must they justify or explain these reasons to you or any of their readers. It's their weblog, they can do with it as they please.
Offensive language and materials
The internet is a place that encourages free and creative expression, and as in any environment where people are given this freedom, conflict may arise. If an author uses language or materials that offend you, leave. Contacting the person or their isp, demanding they remove the content or change their ways is absurd because you are viewing their content of your own free will by visiting their site. Simply stop going there and you won't have to see whatever it is you don't like about the site. An obvious exception to this would be if someone were providing illegal materials, in which case it would be appropriate to complain to their isp or contact authorities.