Build a solid impact and business case
Get your problem clear - what are you solving and for whom, as customer + problem = business case. Think how to make your solution and business model scalable. Measure and manage your impact case. Venture philanthropists are more likely to have a higher tolerance for lower initial profitability and greater risk tolerance, if a solid impact case is present. Try to look for investors who are already passionate about the topic you’re working on.
Gather a team of experienced professionals
As a founder, you need to have prior knowledge and expertise - how did you become aware of the social problem, how deep of an understanding do you have about it? How about the customer's problem? Did you for example work in a big company before which gave you good insights into the segment and the market? If there’s absolutely no match between the company and the founder, then investors won’t believe the person can really understand the market, the opportunity, the solution.
Make sure to bring on board team members with know-how, experience and a passion for the topic. Investors value a strong team with the right mix of skills and a successful track record.
Build a network and make yourself seen
If you don't have a wide personal network yet, go build one - participate in startup events, take part in pitching competitions, go to places where investors meet startups, wear your company T-shirt and introduce yourself. Any personal contact, even for only 3 minutes, eats cold (even perfect) emails for breakfast!
If you get even one investor committed, ask for warm intros. Let them help you make contacts. Also - ask other startuppers which investors make good warm intros and try to approach these. If you get them on board, your work to get the next ones just got easier.
Make sure you have a strong pitch
Practice your pitch and polish your deck, and also create a one-pager - always take the chance to send materials, but realize that investors get several of these in a day. Don't take silence and "no"s personally, move on.
Look for investors that are the right fit for you
Don't go after big VCs in the beginning, they are probably not your match for the pre-seed round. But if they happen to contact you, try to build a relationship for the future. Rather check out early-stage investors, angels, venture philanthropists.
If you just want the money, that’s OK, but if you also need an advisor or a board member, then do your homework - look for people who have an emotional link with the topic, who might be interested in your impact, and have the time. Busy entrepreneurs would probably be able to give you only 30 minutes for a phone call per quarter.