coug60's list pretty much covers everything.
The essential steps are:
1) Fill the gas tank to the limit just before storing. Prevents oxidization and condensation which can rust the inside of the tank.
2) Add a fuel stabilizer and run the car for a few minutes
3) Disconnect the battery or add a good battery tender (BMW's tender or a CTEK)
4) Change the oil before and after. Old oil is acidic and you don't want it sitting in your engine for an extended period. Contaminates can settle to form sludge. You can use cheap synthetic oil before storage and replace it with BMW-specified synthetic when you get back after driving the car for a few days.
5) Park on boards/tire cradles or put the car on jackstands
6) Do not set the parking brake
7) wash and wax the car
If you do not have access to power for a tender I would disconnect one of the battery terminals.
If you cannot use jackstands I would crank the air pressure in the tires to the max rating written on the sidewall. Then park the car on 2x12 boards or even better Tire Cradles (thick rubber mats) to help prevent flatspots. You should not park directly on asphalt as the oils in it can affect the rubber. On concrete it's the moisture. A full plastic tarp under the car is a good idea. If you use jackstands maybe spray the exposed chrome piston rods on the struts with WD40 to prevent rust.
You can also cover the tail pipes (rag or plastic bag etc) to keep air out of the exhaust and engine. Mice too.
While you are gone don't have someone start the car in storage unless you plan on driving it around for 15 min or more at a time. Otherwise moisture will form in the crankcase and exhaust.
Straight lines are for fast cars...turns are for fast drivers
'04 M3 - track
'06 650i Cab - daily driver
'02 Highlander - kid hauler
'01 330Ci - winter beater
Last edited by Yorgi; 01-03-2011 at 09:56 PM.