The GDPR is meant to make life easier for EU citizens, to protect their personal data, both online and offline. Consent was a big topic in the Directive as well, but the GDPR, with all the new individual rights it introduces, it makes it even more important. The Regulation makes obtaining consent a bit harder, while it also makes it easier for individuals to withdraw it.
First of all, you need to provide the person with information with regards to the nature of the data processing – why do you need their data, what will it be used for and even what are the risks if they agree. You cannot include consent among other contractual issues, such as the conditions and terms agreement. It is clearly stated in the GDPR that it must be specific and informed. Silence or inactivity will also not be considered valid as consent.