Aside from the advice already given such as validating your market and raising funds from early-stage sources (i.e., friends & family, bootstrapping, incubators and accelerators), another set of sources that are often overlooked are grants.

Most grants are quite competitive, specific for what they look for, and take time to put together and to receive funding. However, they are non-dilutive. If you are developing a solution for where there's a fit for a grant opportunity, I recommend pursuing grants in conjunction with traditional funding sources.

One major program backed by the US Small Business Association is the Small Business Innovation Research (SBIR) program. This is essentially a $2.5B seed fund!

Here's the link to the SBIR website - https://www.sbir.gov/ - and you can read a bit more about the program on my website - https://caizio.com/blog/

Good luck with your new venture.
Cheers!