When you write your resume, write it as if you're looking to borrow money. You must convince the reader that you're worth the $300-500 an interview will cost. (Yes, it actually costs that much to perform an interview) Make them believe you're worth the investment.
Sell your successes and learn from your failures. When asked about a time you failed, never go into details, just use generalities that don't give too much away. Make sure that you have an overcoming story that shows that you've ensured the failure won't happen again.
Successes are easier to sell, but harder to market. You need to apply your successes to the target company. If you're working with customers, highlight how helping a customer led to an increase in spending for that person. Computers, highlight an efficiency gain that came from your success. Things like this will get you a better chance of an interview.
Finally, get any certifications you can. Even a cheap certificate is worth more than none. If you know something, find a way to get proof that you know it.