From a strictly regulatory standpoint, the answer depends on what sort of tickets you hold, where you sat, the aircraft's type certificate, and whether anyone else was aboard.
Assuming the aircraft requires two pilots, basically, each pilot seat must be occupied by the person qualified to be and acting as the required crewmember at all times (see 91.105(a) for the details). The only way you, a person not qualified as either PIC or SIC in a Beech Premier, could be occupying one of the pilot seats would be if were designated to receive SIC training in that aircraft from a qualified instructor and there were no other passengers or cargo aboard. Then you could log it as SIC, flight, pilot, and training received time. Any other entry that appears to say you were manipulating the controls or even just occupying a pilot seat during flight would be a statement that could be used as evidence of a violation of 91.105(a) and 61.55 by the PIC.
Assuming this is a single-pilot certified jet requiring only a PIC, then there is only need for one qualified pilot to be in the left seat, and anyone can sit in the right seat. However, other than receiving training with nobody else aboard other than the PIC/Instructor, to log that time legally, you would have to hold a Beech Premier type rating, which I gather you don't have. Again, any entry in your log to that effect would raise FAA eyebrows, as there is no standard column in which you could legally put the time.
My recommendation is NOT to put this in your official pilot log. As Henning noted, it won't help you in the future, and all it may do is attract unwanted attention from the FAA to yourself and whoever was the PIC.
