Have you considered creating an AngelList profile?
This is a really good way to learn about investors as well as allow investors to learn about you and your ideas. If you decide to create a profile, include things about who you are, information on your company or product, as well as anyone else working on the business or project with you. It makes it easy for investors to find you.
I would also consider making profiles at the following sites:
The more you put yourself and your startup out there, the more likely it is that and investor will find you so you can save time hunting them down and focus that time into your business plans.
Join the sites mentioned. I have not found any other good ones worth signing up for so these must be the top ones out there. You can also consider getting your branding or idea out to websites like Kickstarter once you have a physical object to show people. Investors are always on there looking for the next big thing.
As silly as it sounds, you can outsource investors in your local area using Craigslist. Don't give too many details but give people an idea of what you are trying to plan and tell investors who are interested to contact you.
AngelList has been promising for a lot of folks I know. I joined this forum coming from another big business forum that got shut down and plenty of folks on there sang that sites praises.