Spread the word - one of the best methods of promotion is word of mouth. Whenever we get a client referral we know that the "selling" part of our job is so much easier. So how can you get referrals:
1. Ask - ask and you shall receive! When you send a follow up note to make sure your product arrived, and they are satisfied with it ask them to send you more business.
2. Bribe them - you can include that if they send you a new customer and they buy something you'll give them a discount or something free.
3. Make it easy - make sure to include your websites URL / contact information where it's appropriate on your product. You may want to include a small free gift like a magnet, pencil etc. Remember out of site is usually out of mind.