I can boil my advice down to three points:
1. Have a clear unique value proposition. Why should someone or some company choose you? What makes your agency “better” than others?
2. Related to that, you need a niche audience. Don’t try to appeal to everyone, otherwise you will appeal to no one. Focus on an industry you’ve worked with or an industry with an audience you know well. Make sure that niche includes businesses that can afford your services. For example, I launched an education service for entrepreneurs and young startups but they couldn’t afford my hefty price tag. So ensure your “product” matches the audience.
3. Create a bunch of sample videos to show your abilities. The first thing prospective will ask is for some examples of your work, specifically for other companies. I’ve been approached by dozens of people offering to handle my video content only to have no examples or one or two personal videos that are completely unrelated to my services… so I was uncomfortable saying yes.
Hope this helps! Video agencies can be lucrative but also have a LOT of competition. Try to stand out on price and the time to complete videos.