Find some relevant publishers. There's a large number to choose from, so it's paramount to find the most appropriate. Companies that specialize in either children's or educational books are the best to go for. Scan through the children's and education sections on publishingcentral.com and make a note of any that may be worth pursuing.
Conduct further research. Publishing Central offers a brief description of each publisher, but it's a good idea to look at the individual websites. Find out what genre of books they have published and who the target audience is.
Make a shortlist. Using your notes from all the publishers you have researched, eliminate any that you feel are inappropriate. Rank the most suitable in order of preference so you can target them first.
Look at the individual guidelines. Depending on the publisher, they will want to see different things. Some may recommend only sending an exploratory letter in the first instance, others may want a writing sample, or even the entire book. Only send what they are asking for. If they don't specify, it's best to send an initial letter with the offer of providing additional information.
Target each publisher. Rather than writing a generic letter, it can be worth the extra time and effort to personalize each one. Use your research to include information you have found out about the publisher and why you feel your book could be right for them.
Make a follow-up call. If you don't get a response in about 10 days, it's worth finding a phone number to ring just to remind them who you are. Start by asking them to confirm they received all your materials, and try to strike up a conversation about the book. Have a list of a few questions to get the conversation moving.
Consider self-publishing. If you're not getting anywhere with the publishers, going it alone can be a reasonable alternative. Place a small order with a local printing company, then ring around some schools and bookstores to see if they're interested in buying some copies. If your book appears to be in high demand, place a larger order to save on costs.