by Jonathan M. Stern
You know now that 3,000 feet is the minimum altitude for this trip with respect to the airway on which you plan to fly. Operational considerations such as winds, turbulence, icing level, clouds, aircraft performance, and oxygen requirements should influence your altitude selection. For example, most light aircraft attain a given speed at a lower rate of fuel consumption at higher altitudes. Above 12,500 feet, however, the FARs require supplemental oxygen. Moreover, ATC generally assigns odd thousand altitudes (5,000, 7,000) to aircraft on magnetic courses between 0 and 179° and even thousands to aircraft on magnetic courses between 180 and 359 degrees. This is known as the hemispheric rule.
On some flights, you also may wish to plan the trip to stay out of the clouds as much as possible. During instrument training and for instrument practice, you may do just the opposite.
On this particular trip, the winds aloft are not significantly different at 3,000 feet and 6,000 feet. Given that you can stay below the freezing level at 6,000 feet (it should be 3° C up there), try 6,000 feet as a cruising altitude. It is entered under ALT (with the last two zeros omitted) in the flight log.