Every ESP will give you tools to create an opt-in form for your site. Generally speaking, the less information you ask for (at this initial stage, at least), the better. The more information you ask for, the less likely your prospect is to complete the process. You’ll obviously need to ask for an email address, and I also highly recommended that you ask for a first name so you can personalize your emails. However, asking for any information beyond these two fields can decrease conversion rates significantly without adding much valuable data.
Marketers don’t always automatically receive notifications when they’ve been blacklisted, so it’s up to the marketer to monitor their brand’s email sending reputation. There are a number of free online resources that marketers should utilize to check their blacklist status before sending an email blast, such as Barracuda Reputation Block List or MultiRBL.