CO is very liberal with their standby rules. call the night before, let the agent know you would like to stand by for the earlier flight because you plans have changed.

most agents will look at a series of codes and tell you if the flight is open or booked even though there are still 10 seats open, they may say, "no, its full." i grew up as a employees son. any plane with 10 open seats is holding at least a family of five.

ask if they will read you the PBT (passenger boarding or booking total). some will, some wont.

that will literally tell you how many seats are sold, out of how many seats are available to sell. keep in mind they can sell many more seats than the aircraft actually holds.

this will give you a good idea about standing by early.