1. Should I choose a one topic like current affairs or only bitcoin or only altcoins discussion or should I post everything here.
Post and comment in threads when you have something significant to add. Before you post, ask yourself: Does this post improve the quality of the thread? Is it helpful? Does it keep the thread going in the right direction?
2. Should the post has old information?
Old how? If you are going to talk about an event that happened 3 years ago and share old articles, no that isn't needed, unless you use that information to prove a point. The information and links you share should be accurate and on topic.
3. Should I post only links which define my whole post.?
Plagiarism is a serious violation on Bitcointalk. Whenever you read a piece of information from another user, a media site, etc, you need to share that link in your post and make sure you do not pretend that what you are saying is originally from you. Always give credit to the author. Don't copy/paste unless it's necessary. When you do, don't forget the source link.
4. Should I reply to every one who reply to my post?
That is not needed. Replies like
thank you, great info, I agree, me too, great job... are low quality posts and don't bring anything new to the conversation. Reply to questions that people ask you, and when you have valuable information or feedback to share.
Little PRO-advice here: there are some Legendary members who are considered "merit sources".
It is not the idea to bother them, but whenever you can you should consider participating in the threads they use to write.
This is not needed at all. Merit sources often watch whole sub-forums in search for good posts to merit. You don't need to look for them. Just focus on your writing and they will find you. If the post isn't good enough, it wont get merited just because you posted it in a thread where 3 other merit sources are active.