"Registration for specialized events" is a very effective method that allows you to gather a more or less specific audience for a specific event. If it is a business conference, then 95% of the audience will be business people, and if it is a seminar on home handicrafts, then the audience will be 99% women, housewives or art lovers. Examples of such events can be exhibitions, presentations, forums, conferences, seminars, webinars and the like.
"Demo or Trial" is another form of email latest phone number database collection where a person leaves their email address in exchange for receiving a trial version of your product or in exchange for receiving free use of a service or product for a certain time ("try 30 days free", for example, some software).
"Free service" is an effective method of collecting a database, since we all love "freebies". For example, "leave your details and get measurements for free", "leave your details and get a third pair of shoes for free", "leave your details and get a free website analysis" and the like.
"Collecting reviews" - you can place a block on the site to collect reviews. For example, "So that you would also find it interesting to read in the blog/listen to in the webinar" - the reader leaves a review and their email. As an idea, you can make a contest of the best reviews, where readers will compete for some prize by sending their review (and email, respectively).
"Joining clubs and communities of interest" is a very relevant topic, as people meet and become friends based on their interests. Interest clubs can also hold meetings, events, training seminars and workshops. These are all opportunities to collect a database of email addresses. Examples of such communities or clubs can be car clubs, football fans, beauty clubs, book clubs, Internet marketing clubs, and so on. You can also create a club or community for your area of activity, for your company. But it should be alive, changing and developing. It should constantly host some events that gather a new audience and warm up the old one.