Like you a ride a 1200 Sportster...so first things first...adjust the preload of the rear shocks to max. Air up the tires to the nominal 2-Up recommended pressures asrecommended in your owners or service manual, typically 34 PSI Front, 40 PSI Rear. The other deal is to practice...A LOT. If you are going to carry passenger and baggage load up your bike as much as possible (I even put bowling ball in the passenger seat or better still on rack out back up high to emulate weight there).
Go to empty parking lot and practice figure 8 than a full circle left and right and repeat...remember to keep your head up and eyes around the turn, until you can do turns close to lock to lock, if not able to do initially don't worry just work to the edge of your comfort level, learn to use the clutch friction zone to smoothen power pulses to the rear wheel while doing slow speed using more rear brake smoothly. Do this in short 20 minutes session, give it a rest and ride regular in town riding practicing using a bit more rear brake, with crisp stop and go's so front end dives a bit, but with foot covering brake and left foot only goes down at full stop. Repeat for a few weekends. Practice with your passenger after you have done this for about a month ahead of time.
Remember, your abilities and skill are for TWO people, so that adds to the mental stress as well. Travel on main roads with your passenger, and daylight clear riding conditions. There will be plenty of time to run into the night riding, inclement weather and bad road conditions as they come...hopefully with you doing solo first so you know the feel and handling of the bike under those conditions BEFORE 2-Up real world exercise.
