By Shirin Oreizy, founder of Next Step.

Maybe you're launching a new product. Or maybe your outdated site is starting to turn away business. There are several good (and even urgent) reasons to overhaul your company's site, design and messaging. But if you don't avoid these common mistakes, that expensive new redesign could do more harm than good.

For a successful redesign, avoid these common mistakes:

1. Skipping the reality check. If you make your assumptions in a bubble, don't be surprised when you eventually hear a loud popping sound. Crystallize the needs and hesitations of all your target markets. Go talk to actual customers. Watch in real time as they make decisions about your company. Are your assumptions correct? Pay close attention to the words your customers are using to describe the issues.

2. Overlooking the psychology of decision-making. You can't afford to assume that people will take one look at a set of facts and do what's best for them. If that were true, we'd all have hefty retirement accounts, get enough sleep and have long ago shed those last five pounds. Luckily, emerging research in behavioral economics and social psychology shows that our irrational decisions follow a predictable pattern. Try to remove friction from the decision-making process.

For one global software company with a high bounce rate, it turns out that too much information resulted in cognitive overload. We simplified their core messaging and added a section called "Who Needs It," addressing the specific friction points and benefits for each of their buyer personas. The results: Web inquiries increased by 600 percent, blog traffic increased by 400 percent, and bounce rate dropped by 40 percent.

3. Skimping on design. Have you placed the key messages in the areas where the human eye tends to land first? Have you made it easy for users to scan your services by marrying them with icons? Design drives behavior. Clients who put careful thought into winning customers' confidence perform far better than those who simply dump all their information on a landing page.

4. Forgetting what it's like to be new. One of our clients wanted to reduce the costs associated with their call center. By asking a few questions, we realized that their users were older consumers who were not comfortable navigating a complex website. We had to make it extra easy for this specific type of user to find specific answers, fast. We laid out the users' most common concerns in simple language. Icons made it easy to scan for categories and the answers were now just a click away. The result: The redesign reduced calls by 70 percent.

5. Adding too much info. Over the years, we've discovered that even the smartest, biggest and most worldly corporations suffer from the "and this" syndrome: They add fact after fact, after benefit after feature. But too many messages equals no message. Be strategic about how you display your information. Let consumers digest the essence of your message before moving on to the next nugget. This so-called "progressive disclosure" allows consumers to control their journey and feel good about their intuitive choices.

6. Relying on slow load times. Consumers won't wait. If your site takes three seconds to load, you risk a 50 percent higher bounce rate. You need build speed into your site from the ground up. Create clean, well-structured code that has eliminated all inactive lines from the files. Make sure that you're working with a firm where developers consistently minimize all files and always size your site's images based on the design. If you use billboard-sized images for postage-sized usage, you're wasting everybody's time.

Avoiding these common pitfalls in a redesign can greatly boost your chance of success. Demand that each element of your new site creates an irresistible momentum and your redesign won't fall short.

Shirin Oreizy is the founder of Next Step, a design firm that uses the latest research in behavioral science to create websites, user interfaces, brand identities and campaigns that drive user behavior.