When it comes to keyword research, it needs a lot of expertise and understanding of the user prospective.

I mostly get confused while chosing keyword for the site, if I opt to choose unique keywords then I can get ranking but they could be so less popular that could not draw enough traffic, but I use keywords that are very common, then I can get good amount of traffic but they are so competitive that its rarely possible to get top 3 ranking for them. I have used Google keyword suggestor tool even but still could not find the best way to justify

Use trends.google.com as well, you can compare the search volume of different keywords and keyword phrases.

If you develop an article then use the keyword suggestion tools as mentioned above, you will then get a better idea of how to "massage" the content so that your site shows better in search results.

Just take a bit of care! Keyword suggestion tools are automated and many of the "keywords" and "keyword phrases" make absolutely no sense or are not relevent to the site. The site in my sig is an outdoor blog and the keyword tools suggested a few things that I would not want to focus on in a "G" rated site.

the best choice is a competitive keyword with a huge searches and a lesser competitor., I suggest google adwords and google suggest as a good tool in guiding you to choose the best keyword

Well......do not go for single or general keyword, it will be better to choose a keyword phrase. Also avoid keywords have heavy competition. Its always better to go for keyords have less competition with higher search volume. You can use wordtracker or adwords tool to select and analyse your keywords.

try google suggest.

I also suggest the wordtracker or adwords,, it is really hard to think of a competitive keywords,, so I hope this two helps..

Jyoti it's a balance in choosing keywords. I think an example will help.

Say you sell blue widgets. The single word widgets is probably searched more often than any other keywords on the topic. It's probably not the most useful though since some people will be looking for red or green widgets and you don't sell them.

'Blue widgets' is probably you're ideal keyword in terms of the traffic it can send, but it's also probably the hardest to rank for.

'quality blue widgets' is a little easier to rank for, but sends less traffic. 'high quality blue widgets' is even easier to rank for, but sends even less traffic. 'high quality professional blue widgets' is the easiest to rank for, but of course sends the least traffic.

Notice though that the phrase 'high quality professional blue widgets' still contains the phrase 'blue widgets' inside the longer phrase. By using the longer phrase you are still optimizing for the shorter phrase. As you gain more links into the page you should be able to rank better for the shorter phrases within the longer phrase.

Also while 'high quality professional blue widgets' might not send much traffic on its own if you use similar longer phrases across your site you can pick up a good deal of traffic overall. By writing naturally on your pages you can also pick up many other long tail phrases. You might gain traffic to 'best quality professional blue widgets' or 'super quality professional blue widgets' by using those other words on the page.

It is a balance. If you don't have enough incoming links aim for less competitive phrases that contain the more competitive phrases inside them and also try to optimize for a lot of the less competitive phrases across your site so you can still bring in a decent amount of traffic.

Also know that while longer tail phrases may not get a lot of searches they are often more likely to lead to a conversion.