Should I refinance my home now or wait?

If your main (or only goal) is to try to lower your interest rate, then it is probably better to go ahead and do it now because in all likelihood, interest rates will start going up before the end of the year. Exactly when is still unknown, and that could always change, but many suspect that we could see the first rate increases from the Fed in September, or possibly December at the latest. So, if you wait another 6 months, you will probably get a higher interest rate than if you did it today - how much higher, I have no idea, but most likely it will be at least somewhat higher.
If you are not really concerned with the interest rate issue, but have a different goal through refinancing, then as Dmitriy mentions, it is impossible to provide a solid answer without knowing the reason(s) you are interested in refinancing.
If you can clarify some of your goals a bit, we may be able to provide a more concrete answer.

There is number of factors to consider before refinancing. What you your goal? Are you trying to lower your monthly payments? Shorten the length of time to payoff your mortgage? Reduce total cost of the loan? Reduce interest rate on the loan? Cash-out/debt consolidation? How is your credit?
Without knowing all of those it's impossible to give you accurate answer.