The list will differ for each kind of business. Spend some time every business day acting on one or more of the items on your list. Keep your mind open for new opportunities. Read magazines and newspapers and surf the Web, always with the an eye towards expanding your marketing efforts. If something strikes your interest, mull it over in your mind and see if you can come up with a way to use the idea.
People buy products and services.
In order to find more customers, you have to find more people. As obvious as this may sound, some entrepreneurs forget that it's all about connecting to people. Join organizations, attend meetings, meet new people whenever you can. There's a fine line between marketing and being too aggressive. Although you might see each person as a marketing opportunity, it is important that you connect to them on a human level without pushing to let them know about your business.