A quick answer. I will expand later if I have time.
(1) Finding VCs: Research online. Nowadays most VCs want to be known, and they have websites and blogs and Twitter accounts. Find the appropriate VCs and send them a short email with a link to your deck. Join founder communities such as YC's https://startupschool.org or https://openland.com.
(2) What to prepare: A pitch deck. https://blog.ycombinator.com/intro-to-the-yc-seed-deck/
(3) What to avoid: Inexperienced startup investors. Also, in the United States, unaccredited investors. Before taking money from an investor, you might talk to a founder of one of their other portfolio companies. Also avoid complex financial agreements: learn about SAFEs and convertible notes beforehand. Overall, you should just review all of YC's latest Startup School materials. https://www.startupschool.org/latest If that's not the way you like to learn, get a copy of Feld and Mendelson's Venture Deals book -- they also run a free online course twice a year.
(4) Common mistakes: Contacting VCs who were not appropriate for the business, location, and stage.
(5) The number one way to increase your chances for getting a VC investment is to not need the VC's money in the first place. A business that is growing exponentially creates its own gravity. Barring that, each investor will have their own priorities. For me, it is the speed of the founder's iterations and progress. That often means I meet the founders long before any serious consideration of investing (e.g., https://bothsidesofthetable.com/invest-in-lines-not-dots-611... )