I am new to some service and wanted to do a study on that particular word. Which tool i shall go for? I tried Google Adword keyword tool but it gives irrelevant keywords which actually lead to spams, junk leads etc.
For an adwords campaign it doesn't get much better than adwords, but you could try keywordstrategy.org.
Go for www.ispionage.com/ tool you can spy on your competitors.. its a paid tool but you can try it for your initial research work for free
When you are going to run a adwords campaign then sure Adwords will work, not only because its a google product but also because it shows more kwds suggestion for PPC. Adwords is the best tool for Keywords suggestion if expect to get more traffic and leads through PPC.
Try kwmap.com as well - it is not quite as in depth as the Google Keyword Tool but I normally find it's a good place to start for broad keyword ideas