Cloud computing (CC) has become a common desire as an alternative for investing in new IT systems, as it allows easy access to a network request to share configurable computing resources.  It helps to speed up and enhance the flexibility of data management at less cost. Many cloud customers cannot choose a suitable Cloud Service Provider (CSP) due to the increase in CSPs and competition in service provision. While cloud computing is widely used, trust becomes an apprehension to everyone who uses Cloud Services (CSs). Despite the critical role of trust mechanisms and methods, rarely comprehensive evaluation methods help the customer select the right CSPs. Thus, the paper's contribution is surveying the main challenges in cloud environments, the role of service level agreements (SLAs), the Quality of Services (QoS), and finally, presents the trust evaluation system to rank the CSPs based on fuzzy logic.