Don't be worried about it hitting it just right, just get a good spread from where you are today. Once you get a 1-1.5% drop in rates it would be wise to pull the trigger (the higher your mortgage amount, the lower the rate change necessary to realize a quick recapture of refi fees). Once you pull the trigger, don't look back.

On a $300K mortgage dropping from 6% to 5%, payments would drop from $1,798 to $1,610. $188x48 months = $9024. If your closing costs are lower than this $9,024 amount over the next 4 years, you came out ahead. (They really should be lower than this, if not, you are getting hosed.)

Same mortgage but on a 15 year term, rate going from 6% to 5%, payments go from $2,531 to $2,372.

There are a few mortgage pro's here that may correct me, but the general rule is that if you plan on staying in your home for 4-5 years or more, pay the points (loan fee). If you plan on selling in less than 4-5 years choose the lower/no points option.

For example, loans on any given day are 5.375% with a 1% fee, or 5.5% with a 0% fee. The fee needs to be calculated as part of your overall interest cost for the estimated holding time to figure your break-even point.

Should be a good time for folks in the mortgage business in the next few months.

Here is a link to a great loan calculator.
Loan calculator