One-to-one is the way forward. Direct contact with people is the most effective method, and the likelihood is that this will be done by emailing (though direct messaging on Facebook or on LinkedIn and elsewhere can work too). Emailing people on an individual basis is, statistically-speaking, usually the driver of pledges. BCC or ‘round robin’ emails sent to everyone allow people to hide behind the anonymity of the other names on the list.
A personalised email has a greater impact, as there’s a greater deal of exposure, and people feel they can’t get away with not pledging! The body of the text can be copied and pasted but top and tail the email with something personal to the recipient. The more you personalise it, the better.
Approach emails methodically; make lists of who you want to email, and work your way through them. Start with your closest network first, e.g. family and friends, and work outwards towards colleagues, acquaintances etc. You will see direct results because of this, which will energise and motivate both you and the campaign. Once other people see your project’s percentage steadily going up, they will be more inclined to pledge too. You can see the list of people who have supported your book, so it can be very useful to mention this visibility in your email, ostensibly to thank people once you see their name appear but also so you can see when people have yet to pledge!
The more names you don’t recognise on this list, the better, as this means that your book is drawing in people from outside your immediate network and therefore your campaign is working well. You can also return to people on email at certain milestones, e.g. 50%, 75% to thank them for supporting so far, to remind/ask them to pledge if they haven’t yet and to share the campaign with their own networks.
Be mindful of your language - ask for support and pledges rather than money or donations. This way, people are reminded that they are investing in a book and become a patron of the creative arts, rather than donating to charity.