They say advertising is, more often than not, the first type of contact between a certain brand / company and a consumer. It is the time when a certain stimulus reaches the senses of the consumer and s/he starts to build impressions regarding the company.And usually, this "first contact" behaves like a first date: it's very, very crucial. So it's also important that the company really thinks their outdoor advertisements through. Outdoor advertising is defined by a reputable business dictionary as "advertising on bill boards, sign boards, neon signs, outside of a building and often by the roadside". So when exposure gets as random as this, a company needs to have a really catchy sign with, if they can, a really catchy phrase.
COLORS
The colors depend on what business you are in. For example, you own a barber shop; therefore, you must not lose the quintessential red, white and blue pole. There are certain color associations that go with every product. If you are selling flowers, put some pastel colors in your sign. If you are selling men's wear, put some masculine colors in your sign. Neon is a very versatile choice especially if your shop opens during the night. Remember, the eyes respond to colors first, then when the eyes like what it's seeing, that's the time when it tells the brain to read what is written.
WORDS
Your sign should be like a mini skirt: long enough to cover the subject but short enough to be interesting. Do not publish a novelette. Experts say the healthy number is 3 – 6 words only. So keep it at that bracket. You will want to stir interest from the people who just happen to pass by and those who have never heard about your company. When they like what they read, they might tell their friends about it. And when you've got a shorter phrase displayed, it's easier to remember. You may use very strong imagery so you don't have to use a lot of words.
ARRANGEMENT
The arrangement refers the whole ensemble. The impact that the sign creates must be very haunting that even when somebody who had just seen it closes his eyes, he'd memorize every detail of it. Use imagery that has a direct association with the product. This is the sum of the how the words and the colors play. Sometimes the colors are right and the words are powerful but they are arranged wrongly. Get a skilled layout artist to do this job and get a lot of opinions from different people.