Communicate with your prospects/ clients. Always. Even if you contact them and they don't buy from you that time. Follow up. A lot of things, issues and circumstances people go through every day, that they might miss a great opportunity such as the one you're presenting.
Don't get discouraged. Follow up. And follow up some more. Contact past clients, present clients, prospects. Educate them. Give out free advise. Have their needs and desires met before yours. Give, consult, share, help, and you will be noticed. It will come back to you.
Obviously don't give away the farm, but small good-will actions, advise and unrquired help will go a long way into bonding with your clients. You have to care about them. You have to want them to be successful. Express your concern about their situation.
Be in their mind constantly so that when they need your services, you'll be their first choice. Develop positive relationships. Don't be a monthly invoice or check. Be a friend. A trusted advisor.
Send thank-you cards for choosing you as their consultant, gifts for referring you to their friends and colleagues, call them up with good news on your service/delivery, alert them on what's going on in the market, give away discounts, books, reports, movie tickets, meals, send them free monthly newsletter, customer awareness guides, etc
The more communication you have with your client, the more trust is established.
When was the last time you did this? It's in your power to strenghten your relationship with prospects/clients. It will take a little time and money, but you will be very happy when you are helping people and getting paid in the process, as well as build a reputation.