I smoked marijuana daily for two years, I stopped smoking at the beginning of April 2014 and then smoked two days at the beginning of July 2014. I have not smoked since then, and have a hair drug screen at the beginning of January 2015. What are my chances at passing a hair 90 day drug screening?

It is pretty good, it may show up the prior smoking, but the levels should be low enough to pass. As long as they are only looking for 90 day usage, that means lower levels from the past would be acceptable if found in test.

Is there anything I can do to better my chances of passing? Other than the obvious, not using marijuana.

Most companies etc... only want to pay for a 1.5 inch sample, going back 90 days. If so I think you have a good chance of passing a hair drug test. I wouldn't lose any sleep over it.