WP-Syntax is the answer.
For example, this is how I highlight an iPhone’s Objective-C code in this post.

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSString *title = [NSString stringWithFormat:@"My %@ syntax", @"AWESOME"]; [...]

A while ago, this blog was not showing correctly some chinese (UTF-8) characters.
It was due to the WordPress that I have set up using a wrong character set. It was using latin1 instead of UTF-8.
To solve the problem, you could [...]