How can I get an admission in top International relations (foreign policy schools) of the world?

Your question is very tough to answer with any specificity. There are far too many variables that go into a decision lie this. For example, your description of your grades as ‘decent’ leaves a great deal of wiggle room. Typically, students accepted to top programs have grades that are superior. In addition, they often have exceptional recommendations, or exceptional world experiences, or both. In the next couple of years you should try to involve yourself in something (I am being purposefully vague here as there are many options) in which you will excel and demonstrate your passion for the field and your ability to add to the program. Some examples would be work using either any connections you might have or skills you already possess that will give you the opportunity to carry out activities that will make you stand out in a dramatic way. It could be an NGO, or with a political campaign or politician, or it could be through some of your efforts using new media. And thre are many many other options in addition to these 3.   How willing are you to put yourself out in the world? If you are a risk-taker, then you might consider going to a hotspot and getting an on the ground perspective while doing some service, research, work or all of the above. For example, if you went over to Bangladesh right now you would find issues-- child labor, religious and political unrest, and economic potential all mixed in. You could, if you are lucky and persistent, get access to some things few would. Or you could end up sadder and wiser about the way the world works. Both of these might help you, but you would also be putting yourself in a place you may not know much about and that might be difficult for you. And it could get dangerous.   It is almost essential to be able to set something up first before jetting off there or some other place. It helps to have contacts on the ground. So talk to friends or colleagues or as many as you can to see about the connections they might have that could help you. If you have other languages than English this might be of help too.