Meta Tags - how long does it take for them to work?

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I just put a code into my site html and was curious as to how long it will take for it to start helping my site get more hits? I'm very new to these and have heard that they are very helpful. Sorry if this question is dumb...I've always been one to prefer hearing others opinions or get actual help from people who have done stuff instead of just looking it up on google. :) Thank you in advance.