Tennis on clay is completely different from grass, carpet and hard surfaces, so it is smart to prepare differently and apply specific actions to increase your chances of successful results. You have to take care of a lot of areas to make sure that you have more than one advantage over your opponents.
Clay is the slowest surface, so the RALLIES ARE MUCH LONGER. It is not a surprise to see two European players having a rally of 20-30 shots, even a few times in a row. Long rallies mean that you need solid endurance, because without it you will start making decisions based on your fatigue level and not on your strategy.