How are people today able to get millions of subscribers within a day? Do they use any secret SEO techniques?
Having millions of subscribers appeals to masses in industries such as entertainment, tech, lifestyle, education, etc. However, it's hard to find a general brand's official business channel having a 7 digit subscriber base.
Having said that, every niche has it's own possibilities. For example, youtuber pewdiepie has around 100 million subscribers. Check out what his channel is about and you will see what I mean. Now take a look at youtube.com/consultease. It's got roughly 202,000 subscribers. It's because of the specific niche and the geographical audience it appeals to.
I'm not saying every channel or brand in a particular niche will reach similar numbers, but this is an important factor when setting expectations and putting together a strategy.
Now for the important part - how do we get the number of subscribers we aspire for? Well, it's complicatedly simple! You have to update content regularly and produce useful content around your brand, product or service, that will appeal to your target audience. This is where you should put your head and heart on.
Bonus tips: On Youtube, you will have more success with a channel representing value-driven content, rather than a channel just pitching a particular business's services or products. You can also search on Google with a site charging $17/250 subscribers. That would add up quickly if you want to increase subscribers