The biggest issue is that when a person gets to this question, they are already behind the eight ball and money has been lost; a house needs to be priced right to begin with!
My experience tells me that you need to find where your house is weak and plug that hole.
Common areas of weakness:
1) cosmetically undesirable
2) structurally inadequate (needs too many repairs)
3) list price may be off (remember that market value changes over time)
4) marketing may be inadequate
5) the commission (usually not a weakness, but can be a strength in the right circumstances)
So if a strong and accurate CMA indicates a fair asking price and your home is "move in ready," then evaluate the marketing. You'll know where you stand with your marketing by how much response you've gotten. If you haven't gotten at least 3 to 4 lookers per week, then marketing is at least one weakness you face. But the number one thing you can do to sell your home (assuming the marketing, price and condition are in line) is to make it really stand out to your potential buyers! This can be done fairly inexpensively.
As far as adjusting the commission goes, this is something that ideally should have been done right to start with. It has a more limited effect once the house has been on the market If you are considering this, try refreshing the home's appearance first. It may be more money out of your pocket today, but it's actually much (MUCH) less than the cost of your home not selling for a long time; just think of all the additional mortgage payments, taxes and reduced selling price.
Overall, my advice would be to hit the house as hard as possible with a makeover, possibly adjust the price (but not too much below what a CMA indicates) and, if it seems best to you, you could throw another 1/2 or 1% on the selling ending of the commission. There's no such thing as "average" or "standard" commission, but I can say that your home's odds of selling increase with the commission... BUT you simply must make sure all the other factors are in line first and use a commission increase as something of a last resort.