What are the best tools to search social networks for a particular keyword?

My question is pretty straight forward....

What are the best tools to search social networks for a particular keyword?

There are several occasions, where a user ask for a particular product/service, but because we are not aware WHERE..... so we loose even we are capable of offering particular product/service

so all i want to explore is there any monitoring tool available in the market through which we can monitor social network, so when a user ask or post anything related; the tool can trigger an alert to us on the basis of KEYWORDs.

I am involving 3 major social networks
1) Facebook
2) Twitter
3) Linkedin

I am noticing especially on 3); that few people are so active; if any user posts asking particular product/service; within few mins they reply to that user and offer their product/services. Very effective way of lead generation as the lead is QUITE HOT, and if you are first to respond, you can convert them into REGULAR CUSTOMER.

Just through some light on this subject....

 

There are many practical and free tools for social media. They fall into three broad categories: watch tools, publishing tools, and account management tools. I do not use them all personally, but you never know when one of them can be practical in a particular case.

5 Standby Tools: Topsy, Social Bakers, Social Mention, Klout, Feedly.

4 Publishing Tools: Buffer, Swayy, Facebook Debug Tool, Knowem?

5 Account Management Tools: Manage Flitter, IFTTT, Social Sprout, Followerwonk, Twitter counter.

There are many practical and free tools for social media. They fall into three categories: watch tools, publishing tools, and account management tools. I do not use them personally, but you never know when one of them can be practical in a particular case.

5 Standby Tools: Topsy, Social Bakers, Social Mention, Klout, Feedly.

4 Publishing Tools: Buffer, Swayy, Facebook Debug Tool, Knowem?

5 Account Management Tools: Manage Flitter, IFTTT, Social Sprout, Followerwonk, Twitter counter.

 

First you have pasted it twice, leaving an impression of CCP.
Second, you haven't addressed my concern.