I've been in the advertising business for over 12 years. In that time I've
learned 3 fundamental truths about advertising:

People will buy from you for three reasons. I call these the KLT Factors:

They know you
They like you
They trust you
It's pretty simple, isn't it?

Truth #1:  THEY KNOW YOU:
It's obvious but true.  If someone
doesn't know you they can't buy from you.  The idea then is to get in front of as many
people as you can with the budget and resources you've got.

Truth #2: 
THEY LIKE YOU.
Prospects will like you for basically a few reasons.  Product Quality or Price or Service. If your product has some or all of the above attributes then you're a step closer.

Truth #3:
THEY TRUST YOU.
Trust comes through in many different ways.
The customer has bought from you in the past and is happy with your service.
You have a product that they trust, and associate that trust with you.
You have advertised to them for long enough that they assume that you're still in business because you're successful.

Here is a scenario of a successful advertising campaign. Keep in mind that you'll always attract somebody
who is in the buying cycle for your product or service right now.  If
they're not interested in your product right now, then it is your job to stay in
front of them until it is their buying cycle time.
You advertise to the customer ONCE.
Unless they are hot in the market for your product right now, they'll probably say, "That's nice to know" and not give your ad a second notice.  As well, they'll very quickly forget you as
soon as their eye leaves your ad.

This is where we lose most of the advertisers.

You advertise to the customer TWICE.
They still say, "That's nice to know".  They again forget you quickly.  You haven't as yet earned their trust because they don't know you.  They haven't internalized your name into their memory.

At this point most advertisers say to themselves, we've spent this much time money and effort and nobody is buying from us.

You advertise to the customer FIVE times.
At this point the prospect starts to take notice.  Now he's seen you a few times and is familiar with your name.  He might not be in the buying cycle for your product, but he is going to give you a try when he is.

Advertisers who make it this far understand that advertising is an investment.  They will get a return on their investment.

You advertise to the customer TEN times.
Now the prospect is saying to himself: "The advertising company (your company) is really diligent.  They've been in front of me for so long and so often, they must really be a going concern."  At this point the customer is more than likely going to trust that you're going to service them well because you're still around and you're still advertising.

You advertise to the customer TWENTY OR MORE  times.
The prospect now says to himself, "This company is a mainstay company.  We definitely can rely on their product and service."  At this point the prospect assumes you're trustworthy and that you're going to give the best deal.  This is where the real return on investment comes in.
Advertisers who make to this level are successful and stable.  They have stream of business and referral that lasts for years.

SUMMARIZED:
MAKE SURE YOU STAY IN FRONT OF THE CUSTOMER OVER AND OVER AGAIN UNTIL THEY'RE
ALMOST SICK OF SEEING YOU.  IF YOU GIVE UP ON THE FIRST FEW TRIES, THEN
YOU'RE NOT GIVING THE PROSPECT A FAIR CHANCE TO USE YOUR SERVICE.

Copyright: Monty Loree - President HomeGrown Advertising Inc (1994) all rights reserved.

About the Author:
Monty Loree has been the principal/president of HomeGrown Advertising Inc. since it began in 1994. He has written and overseen the development over 5 different types of websites. Monty is very tenacious and diligent about searching out and trying different methods of internet advertising. He applies his 11 years of offline/traditional advertising wisdom to his internet projects.