If you are having problems with it these are the things to check.
Firstly, make sure you have enabled the plugin in the Joomla plugin manager.
If you have, are you getting any error message at all? You should make sure that you have the 'Show Error Messages' plugin parameter set to 'yes' as this will help.
If you get an error message saying 'Error contacting Amazon Server' then you are not getting any response from the Amazon Server. In that case:-
Usually you can turn this on by putting a text file called php.ini (or sometimes php5.ini) in the root folder of your site, which contains the line
allow_url_fopen = 1
If that doesn't work then you might need to contact your hosts to ask how to turn it on, but usually this will work.
Any other error message will be a response from the Amazon server. If you are getting any sort of response from the Amazon server then the problem is with the keywords that you are trying to use, they are probably too specific. The Amazon server will return results only if it can find a product that matches ALL keywords that you use. If you use too many then it probably will not find a matching product, so use fewer.
A good strategy is to start off with some very general search terms that you know should return results for example 'silk', 'scarf'. If you don't get any response then you know that there is something wrong with your setup. If you do get a result you know that the plugin is working and you can start refining your search terms.
The plugin makes things a bit easier by only using the first two metatags that you supply (you can change this in the plugin parameters), so that additional ones can be anything that you like. If you want the results to return a specific product a good trick can be to use the product ASIN or ISBN as one of the first two tags - you can find this on the Amazon product page.
You can try going to the Amazon website, picking out a product at random. On the product details section of the page you will see something like:-
ASIN: B005SNSNH6
If it is a book you will see somethng like:-
ISBN-10: 144490602X
Either way this code is that Amazon item id. You can use it to set up the simplest possible code for the plugin, for example:-
{amazonWS:itemId=B005SNSNH6}
Put the code in your article (you can use the code exactly as displayed above, however it is better to substitute the item id for a product found on your country Amazon site, because not all products exist on all Amazon country sites - this one is from the UK site).
Depending one what you see will tell you where the problem lies.