How much research experience or publications are required to get into a good PhD program in USA I am an international student(south Asia) who has recently completed his 4th semester in CS. 

My current CGPA is 3.2 (social science courses in my freshmen year messed it up)  and Major GPA of 3.6. 
I am expecting my CGPA to be around 3.5 by the time I graduate.

I do not have any research experience and I am worried that I might not get into any good program.

My question is that How much research experience or publications are required to get into a good PhD program in US? or that How much experience does an average accepted candidate has? Phrased in a different way:

What kind of experience should I aim to get by the time I apply to grad school that I get accepted into a good program.

I am not talking Stanford, MIT etc but may be among the top 30-40.
I think you should focus more on the quality and focus of your research than the amount. If you are researching a concrete topic, and have 1-2 solid works dealing with it, then you are golden. Make sure you explain the value of these works in your research statement/essay. That would be more or just as important as the resume, because it is an expression of you as an individual.

Other people will tell to go down the bullshit path and sprout several pieces that milk the same research but add little to the field. Some schools will buy that, but others will not differentiate you from the rest of students. You can also try this approach, but it may be even more time-consuming than the first.

Reading your question again, it is better that you engage in research before applying. Perhaps you can contact a professor and work with him, or a PhD student at your university, or find a research institute in which you can put in some time.