It doesn't sound like you are their manager. If not, the first thing you need to do is get management buy-in. Have your development manager integrate the developer's adherence to standards into their employee reviews. You should have enough data points to sell the concept to your boss...the benefits of coding standards are well documented on the web.
Secondly, it's important that the developers themselves have some sort of input into the coding standards. Otherwise, it feels like you're dictating standards out of a vacuum. If the developers have some say into what makes it into the company's coding guidelines, they're more apt to follow it.
Finally, the use of automated tools as mentioned in previous answers will make it code reviews less painful because you can expect, at least, a minimum of compliance.
