Okay, sorry, I do not have any experience operating a Citation in ASE. I have seen a lot of them operating in and out of there, so it must have pretty good performance; in the winter. In the summer, from the people I have talked to that fly Citation 501s, you probably will have to stop at JNC or PUB or one of the Denver area airports before going to your destination.
What ever you do, don't push weight or weather operating in and out of ASE. As I previously posted, I have a great deal of ASE experience. However, even with all that experience operating around ASE I never took that airport for granted, no matter the weather or temperature.
As for departure in marginal VMC weather, I would highly recommend that you do not depart until you can see the 'triangle'. The 'triangle' is the inter-most tops of the mountains that surround the airport. Have a someone there show you what is meant by seeing the triangle.
Don't be bashful or ashamed telling the folks at the FBO that this is your first trip into ASE and try to talk to some of the charter pilots or other pilots that are experienced ASE jet pilots.
Every pilot that has flown into ASE always had their first time.
Now what I'm getting ready to post a point may seem rather stupid and contradict what I just posted about pushing weather, but bear with me. Never use the reported weather at ASE, unless it is just down to nothing, as a final deciding factor for attempting to go to ASE. As long as you have a close alternate with good weather it is worth going to take a look. Another hint is call the ASE tower or FBO and see if other aircraft are getting in when the weather is reported bad. You need to realize that ASE sits at the end of a valley. Sometimes the weather, for lack of a better term, gets stuck at the end of the valley over the airport, but the north end of the valley is wide open and many times you can make a visual approach and never fly through a cloud.
The same can hold true for departure. There have been many days that the reported weather is below takeoff minimums, but there will be aircraft landing one right after the other. Reason, a very thin layer of clouds with poor surface visibility, but when you takeoff you will remain visual for the entire takeoff and climb out. Of course you can only do this under Part 91.
Bottom line; ASE is a very dangerous airport if not respected. Never take anything for granted, always leave a back door open and never, ever push getting in or out.
In truth there has been days that I was the only aircraft (not 121) to land in ASE, then on the other hand there were days that I was about the only aircraft that couldn't land at ASE.
Two best alternates are Vail and Rifle as per driving time, Rifle usually is the shortest.
Oops, forgot one very important thing. ATC non-standard separation on landing and departing aircraft. ASE is a one way airport under most conditions. You land 33 and depart 15, this of course creates the conditions for head on traffic conflicts. Do not be surprised to hear the towner to clear someone to takeoff, heading right at you, when you are on a five or less mile final. The folks in the tower are very, very good at what they do there. The tower will have you stay to the right side of the valley and the departing aircraft to make a slight right turn. I cannot count the number of times I have landed and departed ASE and have passed opposite direction traffic at the same altitude with one or two miles separation. This usually only happens during peak traffic seasons and only in very good weather.
Anyway, have a great trip and be careful.