How do I buy and sell crypto coins?

Could you please elaborate on the steps involved in buying and selling crypto coins? I'm new to this and want to ensure I understand the process thoroughly. First and foremost, how do I select a reliable cryptocurrency exchange? Once I've chosen a platform, what are the key steps to follow for both buying and selling? Are there any fees or taxes I should be aware of? Additionally, how do I ensure the safety of my transactions and protect my digital assets? Your guidance in this matter would be greatly appreciated.