I have been wondering about several ways to quickly gain reputation points.
I tried commenting and giving an "Up" to some of the posts, also tried paying forward my endorsements points to many people but somehow (don't know the reasons), my 8 reputation points became -2.
Also, I got "OP-Kudos" before this post but now I am not getting that one too.
Please suggest me how can I overcome this one.
The single best way to get reputation points is to help people, participate positively in threads and answer their questions correctly. There really isn't a shortcut to better rep, it just comes naturally. Think of it as karma; rep is what the DaniWeb community gives back to those who give to it.
if the goal is to "quickly gain reputation points", you're doing something wrong. the reputation a user gets is basically irrelevant. you should be here either to help learn, or to learn yourself. having a good rep is nice, but if you can't help out people without having the best reputation around, then you won't be able to help them if your reputations is 100.
the easiest way to get positive reputation, is to watch which posts get good reputation, and re-post them with a bit more information, or clearer explanation.
the downside of this is: you won't actually be contributing anything. you may get good reputation of it, but it's not a reputation you earn, it's the reputation the original poster is entitled to.
the good way to earn a reputation, is to add your own point of vue: talk out of your own experience, dare to speak out if you see something that is incorrect in a reply, add your own opinion to the mix, risking to step on some toes, or to make mistakes in your replies as well.
read threads you are interested in, check the earlier replies to see whether someone has already said what you want to say, if so, there's no need to add a five-page-long explanation of what has already been explained. give help the best way you can, and, most importantly, ignore the positive reputation points, they point out you're doing a good job, no immediate need to change there. when given negative points, try and figure out why, just like by asking questions, this is a way you can improve yourself. but in the end, it should be about answering the questions at hand, rather than to "get a treat" every time you did something right.
as for the basic "reputation points", well, you get points each time you reply, each time you log in, ... so basically, just be active on the forum.
The stats are ego-boosters nothing more. You'll also find that you get up-voted, down-voted for no explicable reason. You may get neg reps because the user mistook the downarrow for the uparrow before commenting - I like to think that that has happened to me a few times :)
Enjoy the site for what it is, I tend to ignore the stats, unless I'm in a "dogfight" for a position, and then it's a bit of fun. However, once you start taking them seriously, you may become a 'post whore', which benefits nobody.
As mentioned by others, if you write good quality posts, these stats will improve naturally. It just takes time - maybe a considerable amount of it. Mind you there are some forums (not mentioning C++ - oops!), that seem to give reps for just smiling. Well, perhaps not strictly true. These guys and gals know their stuff. Some forums will be full of fly-byers and noobs, so your chances of getting reps/upvotes there may be fewer. My 2p.