Best Resources For Preparing IMO

    In fact, If you want to join any competition, you need to train again and again with kind of those thing. Mathematics as well, You need to take time, spend time, work hard, keep patience. But, the most important things are resources. 

You need to find the sample tests, sample form of the test so that you can get more understand and also more effective than someone who has no the resources.

Here are some of the resources that I used to find when I prepared for IMO:

• Art of Problem Solving : an online forum for mathematical enthusiasts. It has an extensive contest section where you can always find problems to challenge yourself. In particular, the best for preparation for the IMO are past IMO and IMO shortlist problems, but also some other national or international Olympiads (EGMO, MEMO, USA, Canada, Russia …)
• Yufei Zhao : handouts are also very good.
• Evan Chen's Website : with his awesome handouts.
• Euclid Geometry For IMO : from Evan Chen has recently been published. This book provides a very solid background in geometry. It assumes no previous knowledge
• 14 Number Theory Problems : You can find It in Amazon.
• 102 Combination Problem

I believe the most efficient way to prepare for the IMO is to do as many problems as you can. This needn’t be limited to the problems from one resource so don’t feel obliged to go through one book systematically. (Also, all mentioned books are available on the internet, but I am not sure if legally.)