It is amazing that just by following through on your word you can set yourself apart as one of the top 3-5% of sales professionals (or business owners, as the case may be). Yes, most people mean well, however they do not follow through as promised.
The best of the best learn to under promise and over deliver. Why? Because customers are often amazed when that happens. Too many people make grandiose claims - they talk but don't do the actions to back it up. Therefore, people have become numb to claims and distrustful about what vendors do promise.
Stand out by doing these things:
Be persistent when following up with a company that has expressed interest in working with you. Don't give up just because they don't return your calls or reply to your emails. There is so much noise in the business world these days - you need to follow-up more than you might expect. Assuming the prospective customer is a good potential fit for your products and services - keep some connection to them over time.
Always set a next action when you do get them by phone or by email reply. If they say they are not interested now, ask if you can check back with them in a week / month / quarter / year (depending on your products and services, type of business, etc.) Nearly always they will agree to it, since it is in the future. When you do call, they will probably remember that they'd OK'd the idea of you following up. If they don't, you can remind them of it. It is much better than random follow-up calls whenever. That doesn't work.
If you say you will do something for an existing customer, a strategic partner, or a prospective customer, by all means DO what it is that you said. This is an excellent way to build trust even before you do business as customer / vendor or as partners. How can this be so hard for people to understand? Once you lose trust or respect with a potential customer, you lose your chance to work with them. Be good on your word - do what you say, and if you do - you'll stand out and be one of that "top" percentage of sales reps who also happen to typically make the greatest revenues.
It's not rocket science - and in fact it is so simple, most sellers don't even remember to do these things. Be the difference.